For a non-trials bike, Deore (hydro) is all you'll ever need. Powerful, dirt cheap, indestructible. The more expensive ones (XT, XTR) are basically just a bit lighter, still great but the value for money isn't quite as amazing. Juicy discs are good too, slightly more bite so better for trials but probably not quite as indestructible as the Shimano ones. I've got a Juicy 7 on the front of my trials bike and I like it. Not quite as bite-y as a BB7 but feels a lot nicer. Although I'm not convinced the 7 is worth the premium over the 5 - they're very similar. Juicy 3s ain't so good though. My mate's got Magura Louises on his street bike and they seem OK, but the lever feels terrible, lots of sharp edges etc. I know this shouldn't really be enough to put me off (since the power is pretty good) but it is. I have used 4-5 pairs of Hayes 9s (one on my XC bike for about a year, the rest on other people's bikes) and only one out of 5 has been good. The rest have been really wooden with poor power. They're just about OK on an XC bike but I wouldn't use them for anything else at all.