I trained in Bujinkan for less than a year, but it was a very rewarding experience which informs my martial arts to this very day. It is a library of classical jujitsu technique. Virtually anything you can think of is in there. Whenever I analyze karate and kung-fu forms ("kata bunkai" to Okinawan karate), I often use my understanding of classical jujitsu to ascertain what the purpose of the motions are. And Bujinkan gave me a big leg up with that.
That said, I think it's a dead end in terms of being able to fight well in real life. I say that, because it has an old and flawed understanding of how to train. What MMA / no-holds-barred competition has taught us over and over again is that it's how you train that matters, not what style you train in. I'll explain...
In order to perform well under the pressure of fighting for real, you need to prepare yourself for that by training much the same way. You perform the way you are trained. If you don't train by having someone resisting everything you do, punching you in the face, kicking you in the legs, trying to grab a hold of you and take you to the ground, trying to pummel you once you're on the ground, trying to choke you out, etc. then you simply won't know what to do when you find yourself in that situation for real.
So you want to train with partners who aren't letting you get away with anything. Their job is to win against you. They will stop you from doing anything to them. They will use force. They will not let you do anything. You will feel like it's a fight or a struggle at least.
Now, here's the most important factor: You need to train safely. Because if you don't have rules in place to keep each other safe, neither you nor your partner will be able to come back tomorrow and train. You'll be too injured. So it's vital that you have a reasonable set of rules in place to keep everyone safe.
This is a point of contention with Bujinkan and many other traditional styles. They would argue that they can't do sparring and other kinds of training with people actively trying to "win" against each other, because their techniques would seriously injure or kill themselves if they did. They argue that their stuff isn't a "sport", and so there are no sport rules and no sparring allowed. They say that everything they do is deadly, so there's no way to spar safely.
The counter-argument is that if you don't train with resistance, pressure, and liveness, your skill at actually fighting will be quite low. You will never develop your ability to handle a fully resisting opponent. You won't have any reliable skill at fighting. And when you find yourself in a real fight, you won't know what to do. You'll be a deer in headlights. You might freeze up. Or you might present a laughable defense.
So what MMA and other modern martial arts do is to create a limited set of rules to keep everyone safe, and nothing more. That generally means no eye gouging, no strikes to the throat, and a small number of other obvious rules. But everything else is fine.
When training in MMA, of course, you won't go all out like you would do in a competitive MMA fight. Your goal isn't to destroy your partner. Your goal is to learn from your partner, and he'll learn from you. You don't want to hurt each other. But at the same time, you don't want to go easy on each other, because that wouldn't help anyone. There's a balancing act you need to do. You'll figure it out when you go train at an MMA gym.
While it has gotten more rules over time, the original UFC #1 had almost no rules: no biting, no eye gouging, and no groin shots. This was only enforced by a $1500 fine. Seriously, that's pretty limited!
Bujinkan does involve a lot of resistance, don't get me wrong. In class, your partner will not just let you do stuff to him. If you have to take him to the ground by applying leverage on a standing arm-bar, for example, your opponent won't just fall to the ground when you press lightly on his arm. Instead, he'll wait until you show a strike to his face and until you press firmly on his arm and drag him outwards using the weight of your whole body. Then he'll act the part. He'll let you take him down to the ground. And he'll stop resisting you from this point forward, usually.
Acting is very important in Bujinkan. Without it, partners would have to hurt each other to get the desired response, which nobody wants. So that means you show a strike to the solar plexus instead of actually doing it. And then your partner bends over to show that he would be in pain if he was hit there.
But this kind of resistance and play acting isn't very useful for preparing you for a real fight. You know your partner will always comply if you're doing the technique the way he expects. You just have to use the right amount of force and do the right thing. Your opponent won't struggle against you. He's not going to throw you if you're off balance. He's not going to punch you in the face if you're not defending your head. Etc.
And in real life, your opponent won't often respond to pain in the way it's presented in an ideal way by your partners in a Bujinkan class. You'll be surprised in real life when you punch someone's solar plexus, and yet he doesn't bend forward and stop resisting you like your partners do in class.
Bottom line is that this way of training gives you a false sense of confidence. And the moment you do get into a real fight and things aren't working out like you expect, you simply won't know what to do. You'll freeze. You won't be prepared for someone who's truly fighting back, because that's not part of the training in Bujinkan.
Now, another argument you'll hear from Bujinkan and other traditional martial arts is that if they can't do their eye gouges and death strikes to the throat in training or competition, then it's no longer representative of their art. They're saying that they must have all of those techniques in order to make it work for real. These are apparently fundamental / core techniques in their perspective. Or if they're not fundamental, they're arguing that taking away anything from their art makes it impossible for them to fully express their art, so it's like it's no longer their art.
Whereas the counter-argument is that eye gouges simply aren't core techniques, therefore aren't necessary for sparring. What are core techniques? Core techniques will allow you to get into a position to reliably deliver that eye gouge. If you have a strong core foundation, then eye gouging in real life is a trivial thing to be able to do, because you should be able to get in close enough and control your opponent well enough to be able to apply the eye gouge while your opponent is struggling against you. Whereas, if you have no core foundation, you have no reliable way of getting into a position to be able to apply the eye gouge.
What MMA and other resistance based training methods give you is a core foundation that you can use as a framework for reliably getting in and out of positions while someone is fully resisting and struggling against you. Eye gouges, throat strikes, ear claps, fish hooks, testicle grabs, pressure points / dim-mak, etc. are all secondary techniques that can only be done reliably if you already have a core foundation. Without that core foundation, these secondary techniques are pretty ineffective.
Another argument against things like eye gouges is that, once you have the skills that MMA training gives you, you don't need to do eye gouges. You have lots of other options. And frankly, blinding someone is rarely appropriate. If you're in a war, sure. But if this is a self-defense situation against a bully at school, you have no business doing something like that.
Let's get back to Bujinkan. Like I said, it has a huge collection of classical jujitsu techniques. If that's all you want, it's a great choice. Bujinkan's teaching style is less structured than most other jujitsu styles. White/green belts often learn the same techniques that black belts are doing. And depending on your instructor, it can feel like having ADHD, because they'll cover so many techniques in each class. They don't hold anything back from beginners. That means after just a year of training, you'll have been exposed to techniques that might have taken you a decade before you were shown them in other styles.
But it's a double-edged sword. Bujinkan's training style isn't for people looking to get really polished and refined really quickly. It's a breadth-first method of learning. They don't spend time repeating the same technique over and over again until you're perfect at it. There's no rote memorization. You learn a technique, do it several times, and then move on to something else. You might not come back to that until two or three months have passed. And all the while, they're modifying the technique and changing it into another technique, something they call "henka" (variations). They do this so that your subconscious will just figure out what's common, what the underlying principle is behind the techniques. They won't tell you that. You're just supposed to figure it out on your own over time.
So again, Bujinkan is great for learning lots of classical jujitsu. One of the best styles there is for that if you want to learn lots of stuff really fast. But it's not great for those wanting to get really good at a small number of things before moving on.
And as for fighting, like I said, Bujinkan is a dead end. You won't learn how to fight in Bujinkan. You'll learn a lot of techniques, but not how to use them reliably in a fight. For that, you'll need to train in a manner similar to MMA. Which gives you maybe a plan of action: First train in Bujinkan for a while, and then go train in MMA. See if you can bring your Bujinkan techniques into your MMA training.
There are a number of high ranking Bujinkan people who train in MMA, BJJ, and Muay Thai. You'll want to do some research and read what they wrote about the subject. You'll find a lot of agreement with what I just said. And you should read rebuttals on the web from Bujinkan purists, too. See what everyone says. And in the end, make your own educated judgment.
Hope that helps.