Kimbers and Springfields are amongst the best current crop of mass-produced semi-custom 1911s today. I trust the Kimber more, personally, as I've had a brand new Springfield Loaded pop a spring 1 week after owning it.
Don't buy the Ultra compact, unless you are set on using less than 230gr rounds. 230s don't expand very well out of short barrels, and you should, ideally, have 4-5" of barrel for it to properly expand. With this in mind, I'd recommend that you go with a Compact of sorts - this meaning at least 4-4.25" barrel, and able to fit a 7-round Wilson Combat Officer's magazine (the best) flush.
By the way, the Kimbers and Springfields feel differently if you didn't know. The front strap is more curved and slimmer on the Kimber, and is slightly wider, more flat on the Springfield. It really comes down to personal preference.
One last thing - the two most important characteristics of a handgun, in terms of concealment, are the width of the handgun, and the length/shape/width of the butt of the handgun. The barrel length usually isn't quite as important.
The compact and ultra compact have the same width and butt length/shape/width, i believe. I don't think you'll get that much more concealment out of the ultra than the compact, if any at all.