Voted SP101 because I chose the 4.25"-barrel Commander, not an option in the poll as I read the question, over the 3"-barrel Officer when choosing which 1911 to own.
The Commander conceals, on me, about as easily as the SP101.
Another controlling factor, perhaps playing a bigger role than ease of concealment: Convenience (aka Laziness): The SP101 is always loaded and good to go. I don't keep an auto loaded 24/7 in (perhaps misinformed) deference to magazine life. So, when I decide to get up and go, it's just easier to grab the already loaded snub nose off the shelf than to get into the safe, load, and holster one of the autos.
I like the Commander better, though.