I currently own both rides in question.
I can say this right off the bat, you cant make a wrong choice here, they are both outstanding quads. Both give me a grin from ear to ear from crank to park.
There is nearly no difference in the power or the acceleration of these quads. My wife and I have raced each other on them and every race is so close that there is very little other then who got a better start separating them.
Where you will find a diff, The solid rear of the predator allows it to slide around corners more freely then the IRS of the outlaw which want to plant the tires in every corner.
So if you like to slide the ass end around then you might lean towards the predator...
On rough terrain and steep inclines is where the IRS of the outlaw shines. It will make it up hills that most quads wont, and will beat to the top even those that will.
The IRS is a smoother ride much more gentle if you are the type to sit and ride vrs standing most the time. Its "almost" too gentle...
You best bet is to ride both of them. See which one soots your personal riding style better.
Best of luck and enjoy either of these FAST quad beasts...