You want discs front and rear?
I won't comment on the rear because I just don't know.
For the front I would say if you are 140lbs or under a hope mini would be a great choice.
A lot of people have success with the avid mechanical, but they require constant adjustment.
any magura will leak, but they lock well
Hayes lock decently but in my opinion they just feel like poo and I believe the standard ones are pretty heavy
The conclusion I have come to is that there isn't a good disc yet for trials, but my roomate just ordered the new hope mono and he or I (or both) will be sure to tell you how that turns out whenever it gets here. I have HIGH hopes for the avid juicy 7, but it isn't exactly released yet and it's going to be expensive
, so it's basically not really an option.
If you do get a hope mini, I would definitely recommend at 180 or larger rotor, same with a hayes. The avid is a toss up, and the magura doesn't need a larger rotor. My next front disc is going to have a 200+mm front rotor regardless of which I buy, I'm tired of a front disc that doesn't hold when my front is over the edge of a ledge or down steep natural.
I KNOW other people will have opinions on this