There is a thread with this topic in this section. IMO Karakal are very good replacement grips. Don't mind the balance point. It's nearly useless. the headmass of your racket matter if it comes to power issues. The best way too get more Power is too find your ideal string setup, racket flex, a correct grip size for your handsize and the most important thing is the technique.
Like just about everything else in badminton, the best grip is whatever you find most comfortable. Personally, I prefer a slightly thicker grip so I'll either put an over grip on top of the stock grip (quite liking the Prince ultrazord stuff) or replace it with a tennis racquet grip (which are typically a bit thicker).