From listening to the different demos, to me all of the most recent top-end arrangers from the major manufacturers Korg pa1x, Roland G70 Yamaha Tyros 1 and 2 and Gem Genesys all are comparable in terms of sounds and styles.

I think the differences are the hardware (76 keys v. 61, touch screen, good key feel or no good key feel …), the differences in some features (sampler or no sampler, rootless chord voicing or not hard disk recording …) and how well a particular manufacturer integrates all the features, sounds and styles (easiness of the OS).