Round butts are easier to conceal and have smaller grips. Round butts are mainly on the shorter barrel guns for that reason. There are grips that are made for the round butt that make it into the square butt profile. In addition Hogue makes a grip that completely wraps around the round grip. I have both and prefer the round butt because of the versatility. As for the NY trigger setup I can't say, I've never handled one.
Here's a toast to our wives and to the women we loved. <pause> May they never meet.
The M1 Garand rifle is the best battle implement ever devised by man.