In a combat situation, mag capacity is a concern. However, I REALLY have trouble with the idea that LEOs need great, big mag capacity. If you can't get it done with, say 10 rounds in your pistol (being generous), I'd say it's time to pop the trunk and bring out the shoulder fired hardware, or call in the experts, (ERT, SWAT, whatever they call their psuedo elites). YES, I know, MPs deploy, but the same scenario holds. In most cases, your pistol is used to fight your way to the rifle you should have never stored out of reach anyway. Special occasions will require special measures, of course, and you don't always have access to other systems, but I have trouble with the idea of 13 or 15 rounds flying around without the perp ceasing activity.
I'm not slamming LEOs. They have budget constraints the same as everyone else. We'd all like unlimited range time to hone our skills. The standard answer is 'no money for ammo' or 'no overtime allowed for ranges', but the same bean counters say nothing about spending millions on the new flavour of the day sidearm without considering whether it's needed or not, just that it's cool and someone says we have to keep up with the Jones'. Ammo and markmanship time is what's needed, not new hardware. The Hi-Power served well for many, many years and held 13 rounds. How many times did MPs have to pull and use them, and use 13 rounds? (Perhaps one of our resident Mil Pol can site us a case or two and the end results?) I'll wager not as much as civvie LEOs. Yet I know many of civvie LEOs that have never taken the service gun from the holster, except to clean and range practice, their whole carreer. The upgrade from the Browning, and others, was justified in many cases for the ability for a first round double action pull. On the civvie side in most cases, all shots are double action only long, draggy, pulls to ensure the courts you really, really meant to take the shot. With the Sigs that's not an issue. So what's the big deal with these constant changing of toys?
Just my $00.02, and shooting 5-7,000 rds (pistol) a year and owning almost more iron than the CF doesn't make me an expert, nor do my deployments. Just sayin'.