What type of riding are you doing?

Each silencer is designed for different reasons and will perform differently. The Q and Turbine Core are both USFS approved spark arrestors. As a result of their design, either will "tame" the power a bit. You'll need them if you are racing enduros or riding in national forests. The Shorty (which is a variation of the Power Core) is designed to increase bottom end power, and is best for short courses or woods trails where you won't be revving the bike out as much. The Power Core 2 is FMF's all-purpose silencer, claiming to increase power all around.
My personal experiences have been with stock, Q, and shorty silencers. The Shorty definitely lives up to its claim of enhancing the bottom end ... the bike feels more pipey with it on. The Q really quiets the bike, but apart from it's forest-legal status, I wouldn't choose it personally because it does stifle the bike a bit. I hear the Turbine Core is better for power delivery than the Q, but I've never used it.
Hope this helps a little.

 

i am doing trail riding but i want more power before the power band on the bottom end, so i will get the shorty. what about the fmf fatty pipe. it is the big part of the exhaust.

 

I like the Fatty/shorty on my 125. I tried the Q for trail riding and didnt like it. It took all the snappiness away and robbed me off some bottom end.

 

Ive got the fatty on my 250 and a DEP pipes silencer and it pulls quite good all the way through the revs