The audio drums on the S950 and T5 or of course very good. They are, however, pretty specialized for the particular song or genre for which they were created. I really liked the jazz and swing audio drum styles. Problem is they make the Yamaha midi drums pale in comparison. It's probably just me but without a LOT of tweaking Yamaha drums just don't sound live enough.
Captain Russ, who can afford to buy any arranger every made, or all of them for that matter, still uses Solton (Ketron) MS 60's. He primarily only used bass and drums from his arrangers. They have always had the drums right, in my opinion. I remember they blew me away on the old X1 even.
I have no problem with drums on Korg or Roland. Yamaha and Casio need work. They should sound good out of the box!
I'm going to catch hell for mentioning Yamaha and Casio in the same sentence aren't I?