bb5 or bb7. hydraulics need bled and mechs don't. less maitenenace and less cost. if money is no issue then get avids or magura nd throw as trixer hydraulic brake gyro on with it. that would cost probably 800 bucks but would be mint setup.
simplicity is the key it may not be expensive but xt v brake, linear cable + xtr leaver i run feel nicer than some hydro disks i have run and loads cheaper + a v brake mounted under the seatstays is alot cleaner looking than any disk
i run a juicy 7 on mine, if anything its too good, very little modulation, its either on or off, which makes manuals nigh on impossible (atleast when you are trying to learn them)