I have some XT (m765), some Hayes HFX9s and some older M4s. Have also had Juicy threes and Mono Minis.
Between the Hopes and the XT, rotors are 180/160 (XT) and 200/180. I'm guessing, factoring in rotor size power is probably about even. Hopes might be a little better in terms of modulation but it's not a fair test.
The advantage of Hope is you can buy parts. If you bend a lever blade, or the pushrod you can get new one in a matter of days, and they carry bits for older designs. Getting spares for my m765s is impossible I believe. Also pads for hope are easy to buy.
I'm not a fan of Avid (or to some extent Hayes), bleeding them is a right pain in the proverbial, unless you have the bleedkit with you, you can't just pop down to Halfords and get some DOT.
I don't know much about maintenance for Magura or Clarks.
Friends have Shimano Saint. Power is amazing, but maintenance might be an issue.