Sawed off Gov't models and concealment.
There are four configurations of 1911 type handguns, two are usually reliable, the other two are a crap shoot. They might run, they might not.
1) Full size, 5" Bbl, Original size, usually reliable.
2) Commander, 4" or 4.24" Bbl, usually reliable.
3) Officer, 3" Bbl, Can be kinda iffy.
4) CCO, 4.24 or 4"" Bbl on an Officer frame. Also a crap shoot.
The part of a handgun that's the hardest to conceal is the butt, or grip. Barring ridiculous barrel lengths, of course. In reality, the two smaller sizes, Officer and CCO, don't gain you anything because the butt is at most .5" shorter than a Commander or fullsize.
Newer JHP design has taken these microguns into account, so there are bullets that will get reasonable velocity and expansion from a 3" barrel, but you're not gaining anything meaningful and potentially giving up bullet performance.
Each manufacturer has a slight variation on the designs, but the basic platforms fall into one of the four categories. Personally, I see no need to own one smaller than 5", but many consider the Commander more comfortable to carry IWB.