I like the way DJ Player is built from the ground up, not trying to emulate real life gear, but using the touch capabilities of the iPad. As such it does require a bit of a mental switch to work with.
It certainly has some clever ways of integrating kill switches and such.
And I have played around with the NetOut functionality so you can hook up your headphone to your ipod/iphone wirelessly (really funky running around a venue with your cans around your neck and they are actually functional :-).
It works like a charm. I think I had to dial in about 10ms delay on the mains to sync it but then it works. So no more cumbersome cans cable to worry about!
Lots of possible setups, controller support, etc.
I have used (and liked Algoriddims DJ), but right now my money is on DJ Player.
Greetinx,
C.