The Reax is a smoother motion overall than the Sync. Both balls are able to handle quite a bit of oil, however it seems to be a common theme where the Sync is more useable on a house shot than the Reax.
I'm actually not too sure on the comparison of the Reax Pearl vs. Nano Pearl. Both provide strong backend reactions, but I believe that the Nano Pearl could possibly handle more oil (not be so squirty) if you were to change the surface