I bought mine before I ever even knew about this forum, so I had little to go on when making my decision as well.
My original instincts told me to go with HMF (the one I knew would be good all-around) or Yoshimura (since they're known to perform on similar sized street bike motors) or Curtis Sparks / CT (known for crazy power gains and expandability).
Well, I saw Trinity's ad and went with them on looks, ad claims, future expandability, good price, and just to be different.
Price = 8)
I paid $450 (pipes+shipment :thumbsup

for the pipes, but they got their money back when I went with their EFI controller. It's not necessary to go with their $250 pre-programmed controller if you can tune a $180 Dobeck to spec. (wish I'd known that before)
at the time I was comparing price it was something like HMF $480 P+S, Yosh $505 P+S, CT $580 P+S
Installation =

they're tricky to line up the way you want since they're not one-way bolt on...
I took a long time to get mine line up to where they clear the clutch line bracket AND clear my rear plastic. and there's still a leak at the joint.
I was told to let the exhaust heat settle the joint together, still not happenin
I was told to get a pipe expander, no luck finding one that fits
Sound = :brick:
Loud, but a clean kind, not obnoxious. A good roar... until you let off the throttle, then it chirps
Performance = :burnout:
you can look at the header design and pretty well tell it's a bottom-mid performer.
throttle response becomes so instantaneous, it's ridiculous... it scares my friends, and I myself barely have control over it. I need a steering stabilizer because of what bumps/roots do to my steady hold on the throttle.
after the rush of power from the bottom, she's at home hanging on in the mid-range, great starts in a drag or at the bottom of the hill, she overpowers every obstacle
after feeling all that, you kinda wonder what happened to the top end, why doesn't it offer the same thrill as the mid range?
but the overall power made me change my mind about going to a big bore in the future, I do aggressive trail riding, and going BB would just be shooting a squirrel with a bazooka :rocket:
If I were to do it all over again, I do believe I would have gone with the Yoshi based on similar performance claims and better sound and better fit and finish, or the CT based on their rep for monster systems.
cha-ching
my .02