I asked a bunch of questions at SHOT with the LE reps for the guns. The RDS, not so much. I shot the guns this past week at our range, with the exception of the FN, as we didn't have it yet.
Admittedly, I went into it a bit cringy about the Sig. By the time I was done, my opinion had changed.
M&P was the Core 2.0. Nice overall, but, oddly, the felt recoil was more than I expected. Most officers gave it high marks.
G45 MOS was, well, a Glock. The trigger was the best Glock factory trigger I have experienced, crisp reset and break. I really liked it. The full size frame and compact size slide really was not that huge of a change, or really noticeable. The ambi slide stop/release is new, but still not really a big deal, as it is still about the same low profile, and being a lefty, I have adapted to using strictly right handed guns. A Glock is a Glock is a Glock. Meh. The average shooter officers like it because it is what they know.
Sig P320 Pro. Our sample had the full size, small grip size frame, full length slide, flat trigger. The trigger will take some training time to get used to, but I liked it. I was very happy with it, overall. I am pretty consistent with my shooting, and my groups with the Sig were about 1/3 smaller than with the other two. I haven't used any Sigs since 2005, and I had forgotten how easy they are to shoot accurately. The 320 is very friendly, and I was impressed. About my only complaint is the magazines need more witness holes.
I had forgotten just how much the Glock feels like a brick in your hand, until I shot it side by side with guns that are actually ergonomic. It was glaringly more uncomfortable. If I had been told to choose one, and leave with it (with no other metrics), I would have chosen the Sig.
I also shot the Sig Romeo 2 and the Aimpoint ACRO. This was my first hands on with RDS, and I don't feel comfortable giving any input about them without much more extensive training. They left out the DP Pro, saying the new Romeo 2 is basically the same, only beefier.
Personally, I think the Sig will appeal more to the diverse sizes/shapes of Officers simply due to the modularity. But, it's all going to boil down to money. Our UTM program is set up for Glocks. Switching may get spendy, as we use the UTM system extensively. I'm pretty sure that will be a factor.
Nobody has any idea of what direction this will go. Regardless, whatever we get will be my last issued duty gun, as I plan to retire in a little over 5 years.