Yohan; if you put calipers on an ultra, pro carry, or Target model Kimbers, you would find them Identical for width (grip panel to grip panel) and the reach ( front to rear) reading will be the same, and I am not sure but I believe the trigger length will be identical as well.
The difference is how many rounds they will hold, the ultra will hold 1 rd less than the Pro Carry or full size,and the frame is shortened by that margin, IE more or the handle will stick out the bottom of your hand when shooting a PC or 5".
I prefer 5" guns some people (a lot of people) prefer the 4" pistols
they will both fire about the same but are not as temperamental as the ultra (which is a very reliable pistol but less forgiving of limpwristing).
you can get thin grips, and shorter length triggers, and arched or angled mainspring housings, plus different styles of grip safeties to perfectly taylor the pistol to your hand (if it is not already a perfect fit).