In a first, the Army’s new handgun will be issued to team leaders

Maybe it's a first in light infantry. It's not a first across the Army. In every unit that I've been in every one that wasn't a fobbit was issued a handgun.

And Sigs are a top tier firearm.

I've always been hesitant to join a "camp" on the issue of which sidearm is best. I've fired the M1911 .45 ACP in training, carried the M9, and fired a variety of other semi-auto handguns of various calibers, finding each to have "pros" and "cons". I guess my limited field experience would suggest that the M9's overall ergonomics, weight and age (particularly that rotating safety) present "dated" tech...but neither would I have wanted my regular CC weapon (M&P 9mm compact) in Afghanistan.

Ultimately, I tend to go with what a very skilled (and patient) SNCO told me at Ft. Riley once...if it comes down to needing it in combat, the best characteristic is that it fires as long as you can pull the trigger.

I think everyone should have a pistol as a back up weapon. I always managed to have one but sometimes I caught hell because I did.