All the sensorless brushless motors will have 3 wires, it's probably just the angle of the picture that makes it look like it only has 2.
I wouldn't get a 7XL...well I wouldn't get a 7XL again
. Mine got fairly hot in 5 minute races, but the bad part was that it killed 2 quarks because of the power it used. I haven't used the 8 or 9xl, so I'm not really sure what would be better, but I would get the smooth canned version and an rc monster heatsink clamp to stop it falling apart on big impacts.