I like Dave Leipmann's response where he makes it clear that you improve with both skill and power / strength training. You combine both for the best overall effect.
One of the comments I often hear in BJJ circles is that women often learn better / faster than men, because they don't have the muscle strength that men do. And so they will stop and try to figure out what they're doing wrong rather than trying to power out of something like guys do more often.
But that doesn't mean that men (or women for that matter) should avoid power lifting and other supplemental exercises outside of class. It just means you have to watch yourself. If you find that the only way you were able to get out of a hold, for example, was to power through it, then make a mental note of that. Later on, ask others how it could be handled better using less force.
Make a habit of that. Always ask questions. Never be satisfied with your result. Always look for a better, smarter way. Ask yourself why it took so long to do something. Could you have reduced it to 4 steps instead of 5? Was your opponent off balance or unstable in some way that you could have used to your advantage? Etc. And at the same time, outside of class, work on your physical attributes.
There's a time to go all out and use all the force you can muster, and generally class time isn't it. Class time is where you learn how to do something better. It shouldn't be about who's stronger, who's been lifting like crazy in their spare time. Leave your pride and ego at the door. You're there to learn. Don't try to make up for a lack of skill by using power. A much weaker student might actually be able to show you something you can use if you let him/her.
At a competition, yeah you should go as hard as you want. That's an appropriate time. Rolling after class with someone who also wants to use more power, yes that's fine, but maybe it's best to make that sort of thing infrequent.