Speaking from my experience, the 3" Kimber out performs the Colt 4 1/4" in both chambering and accuracy. With a .452 LSWC the Colt chokes and fail to chamber but the Kimber does not. I was quite surprised as I was very leery of buying a Kimber due to the FTF problems one reads on the posts.
On accuracy from a rest and using Barnes 160 HP bullets @ 1,000 FPS measured 7 ft from the muzzle the Kimber was less that 1" at 15 yards where the heavier Colt (O4012XSE) was 2" group. Now the colt only had 50 rounds thru it and the "matt" finish of the stainless parts and trigger was very rough feeling (yes I had cleaned and oiled it liberally) so I am expecting it to improve. I noticed that the Colt 80 series seemed to hang the trigger (malfunctioning safety?) on occasion and I had to stop and deliberately move the trigger forward or so it seemed, to clear the malfunction. It is also shooting low for me. Novak white dot sights so I need to investigate that.
I believe the Colt will break-in and shoot fine (if not it is going to have a factory visit). All in all, if you are only going to shoot a little then get the Kimber. If you want a Colt then send it back for a tuning and I am sure it will be fine. This is based of me owning and shooting both, I was disappointed with the Colt