I would figure it's a personal preference billt. I don't like the grip angle or texture of the XD. Even though it's a damn fine pistol.
Same with the Glockenspiel 21 I own. aka railroad tie, with grip.
However, as the Sigma were an attempt to rush something out to keep up with G's, the 4006,4506, and a couple other 4series were all steel, and except for the Clintonista "no fire without mag crap" are still holding their value today.
I had a original 411 in .40. bought in 93ish. Trijicon sights, and shot the crap out of it. Never an issue.
The M&P (I own two), have a better grip texture and angle that the OTHER maunfacturers had to play catch up with, as M&P came out with different size grip panels first.
All in all, regardless of brand, the Gen 4 Glocks, XD's, Sig's, etc,... are good pistols...I've also seen $2200 Kimber's fail to eject and feed. I won't change my opinion about my M&P's as I've run them hard and they keep going.
I hate it for rat, and am certain he'll get one that works for him.