I rented the PSR S900 and initially loved the styles, super articulation and mega voices, but after a month I found the styles seemed a bit like playing a midi file. i finally bought the pa500. Although it lacks the sheer number of styles, its style sounds always always seem more real, to me and my family, and my son who is a performer. However you must be aware that importing new styles, and especially transferring styles from say Yamaha, is a very difficult process. Third party pc based importing software has struck a brick wall due to Korg's slow response to the request for releasing the compression/uncompression coding. To see more on this issue visit http://www.korgforums.com/forum/phpBB2/viewtopic.php?t=34700
If you wish to create play lists for performing, you may wish to ask the members there how they make out.
regards and best wishes in choosing the better board,