Hi Stephen,
Korg actually did a survey of what customers wanted over on the Korg forums, 2 to 3 years ago.

Strangely enough, I ended up with my very short wish list.
A fill system similar to Yamaha ie 4 fills which could be set to automatic, with the option of 4 dedicated fill buttons if I wanted to to trigger my own fills.

The other was a bit more obscure, sets of XG mapped drum kits, to suit psr drum mapping . Got that too. That really made manually converting some of my psr styles across to my PA3x , so much easier.

Actually if you agree that the PA3x styles appear to sound better than the PA800 styles, may also have a bit to do with their new Guitar Mode 2 style record function.
They've greatly improved it with the option of having midi notes as well as guitar mode notes on the same track.
Used to be a case of, if a style part ie accomp 5 was set as a guitar mode track, only guitar mode notes could be used thruought the style on accomp 5. Now that one can have a mix of guitar mode & midi notes on the track, maybe it just sounds a bit more realistic ? I don't know, but for an amatuer like me, it makes recording a guitar style track so much easier..

The overall layout is so much better. Not having to go thru 2 or 3 button pushes to get to the correct style bank. Was a tad messy.

Anyway, good luck with deciding what to do.

I had a quick look at a T4 before I bought the PA3X.
As much as I luv the Yammie styles, I'd miss the style creation & editing functions on korg.