For those who have shot both, is there a measurable difference in felt recoil and muzzle flip between the different barrel lengths? Any felt differences?

Measurable? yes. Its subjective but the recoil impulse is different. I prefer the carry but I like the sights better on the compact.

Not much help am I.

i have large hands so I prefer the full size grip of the x carry. the additional barrel length/ sight radius makes it easier to shoot for me. But I wouldn't give up my xcompact either

Six of one, half dozen the other. Do you want 15 rounds of capacity, or 15?

Most of my compact frames, I've switched for "carry" length, and am presently using the Wilson grip module. I do have the carry length x-grip as well, in the Sig factory, and the Grayguns sculpted versions.

The Carry and Compact are the same slide, just different length frames.

The x-compact is actually a subcompact slide on a compact (15 round) frame.

The beauty of the P320 is in under a minute, you can swap the grip module and turn it into whatever you want. You can get a carry, and throw an x-compact grip on it, or the wilson grip, or new compact grip. There are several good choices. It's a little like having several pistols, or at least pistol options, in one.

I have both and the fullsize (FS) in 9mm. I shoot 9mm 147 grain (TMJ and G2) almost exclusively. With that load I don't really feel a difference in recoil. I did decide that I liked the X-compact frame with the 3.6 barrel better than the 3.9 compact barrel. I also found that the longer FS barrel shot better than the 3.9 inch compact. YMMW