I don't think it's a question of style as much as it is a question of brand. Asking "fixed or mechanical" encompasses too many variables to be answerable. Personally, I prefer fixed heads since it's just one less variable I have to worry about in a game loaded with them. I'd hate to hit a deer without the blades opening up. Even if they open 90% of the time or better, it's just another "what if" that's unnecessary IMO.