Hey,
Good call on going with Hydraulics. I went through that delima a while ago and w/o a doubt ended up getting some Hope Mini's. Those Magura Julies are supposed to be pretty good. I havent ever heard anything bad about Magura's except for not too long ago they used to use a fluid which heated easily, but that's solved now.
The thing is i'd go ahead and get something that your mechanic is familiar with because in the end if you cant figure something out he'll be familiar enough with the system to pinpoint the problem. Other than that i feel with Hydraulic brakes that Modulation is the most important aspect because you know they're going to stop you quickly, the modulation is what seperates the good ones from the bad ones.
Oh ya, hayes are nice but i think they're over rated