I recently switched from a medium Bannatyne to an extended small, the only difference here is in girth, the extended small is only 1.5" smaller in diameter.  The difference is noticeable, although I'm not sure it is an improvement but I've only been playing with the new bag for a couple of days.

I'll probably need to make some drone reed adjustments, but so far I'm managing OK.  My current pipe bag cover is a tad loose and that may be contributing to some of the difficulties I'm having keeping the bag tucked up under my left arm, though I'm going to try a few safety pins to see if that makes a difference before I go out and order a new bag cover.

I like the Bannatyne hybrid bag because it is a synthetic bag with a hide exterior, has a zipper for easy access and feels like hide without the hassles of bag seasoning and all that.