Well, blue has hard draw advantage, but for the mana, black can't be beat, though you bleed for it. When I ran Phyrexian Arena, I had some way of getting health back. Usually it involved Spinning Darkness, Bloodchief Ascension, and in the past, Vampire Nighthawk. Then you could stack arenas and draw 3 cards per turn, etc.
I didn't get good results with it, and sometimes I'd get killed by my own Arena lol. I suppose your mileage may vary, but mine sucked so... :eek:

