Bounce beam should be easier to install, because all the wiring would run down the same side. There's a trade off though.
Since the beam needs to reflect off of a ball in order to work, it can have trouble with some dark color shelled paintballs. Most of the time it will be fine though, and I think after a certain delay the T-board will fire anyway.
Breakbeams rely on the paintball to interupt the beam between the two eyes, so paint color is never a problem. But on the same token, if they get dirty from one reason or another they will think there is always a ball present.
As another point, I think I read on OtterSC that on a break beam install you can just drill straight through the body if it's in a press and the eyes will align perfect.
Speaking of Otter, his site is a really good source of Spyder information, and he has a section on just the T-board, as well as a few others. You should have a look at it.
http://www.ottersccustoms.com/t-board.html
Bouncebeam vs Breakbeam
Bouncebeam vs Breakbeam
