Yep... comparing arrangers without taking price into consideration is just not realistic.
Well no really,
The issue here is the implementation of the Audio Drums. If the Yamaha Audio Drums can't edited (they can't be edited, deleted or created from scratch) then the PSR950 users will be limited to use audio drums in styles created by Yamaha.
No the case in the audya where you can take any MIDI base style and create a new one by inserting audio drums on it. You can replace for example an 8 beat style for a 16 beat one in a couple minutes and that is only a small example of all the things that you can do with audio drums in the Audya.
At the end you are going to have to purchase so many audio styles and voice and expansion packs from Yamaha, that the final cost will be the same as an Audya and you don't have to reboot !!!
And remember the Audya have audio guitars samples too.
The next Tyros, Tyros 5, will have the same limitations as far as editing.