Hi,
My vote is for the larger one as the layout of the button functionality is (to me) way superior both for live and studio use.
As I wrote earlier, I do like Tylerhb's expression pedal idea but I do realize that it may be difficult to implement as it will be hard for Kemper to compete price wise due to economics of scale. So my suggestion is for Kemper to design and manufacture a plate that you can screw on to the floorbord and on that plate you can mount your expression pedal of choice. You want 2 expression pedals? Buy 2 of the expansion plates! But maybe this is too simple to be working effectively.
Cheers,
Mats N