XDM with night sights is was what I tried to buy a few weeks ago, but they don't make it in 357Sig yet. I have had glocks and handled a few M&P's, and if I'm buying a pistol of that type, the XD and XDM are what I go to. To be honest, they would probably both serve you perfectly, but I've found the XD/XDM to be my choice.
Why did you decide against night sights? I have heard people say they are a gimmick, but I find them quite useful in low light. Sights you can see are better than sights you can't. IMO