Their programability and software are really nice. Also, their customer service and warranty is second to none. I have a few boards, 2 have XL2's, one has a monster 2, One has a monster 1, the other has a hobbywing ezrun. Have had the monster 1 in service almost a year with no issues.
On the xl2 I'm running 30v (8s) all of the others are running 22v (6s)
Hobbywing EZrun pro's are great esc's too. Their programming is slightly less nice, but they're really reliable and smooth running.
Also note that 6s is pretty much all you need to be able to climb average hills and carry 30+mph speeds. My 30v board has done 46mph. I honestly can't see the use for 8s or 10s boards now that my speed lust has worn off.
I think the main reason you want to 10s or so is to get the motor to the optimum RPM and optimum voltage. Of course gearing, etc can effect that per vedder 8600 or thereabouts is where 50mm to 60mm outrunners perform best.