Sorry but this is far from the truth. Their smiths were returned because of multiple reliability problems with the frame mounted decockers.
Sorry, PAT, but you are far from the truth. There was a reliability problem with the 1076 when it was first issued to the FBI due to modifications the FBI demanded S&W make. (Sounds a lot like NJSP and the SW99--the agency screws up and S&W gets the blame). The problems were quickly remedied, and the 1076 became one of the most rugged and reliable LE weapons available serving in the bureau and other LE agencies (and still in service, I might add).
As for ammo availability, if I were to use your technique, based "an [sic] observations based on my informal visits to gun shops and from scanning the internet," I'd say the 10mm is in better shape than the 357 Sig. In the local stores, ammunition for both is a little hard to find, and when you do, there's usually only a limited variety--though normally at least you have choice between Remington and PMC FMJs for the 10, and you are stuck with Speer for the 357. When you go to the internet, it is a different story--there are far more varieties 10mm available (roughly twice) than 357 Sig.
As to weapons availability, I haven't seen a lot of either in any gunstore recently though the last time I was in the nearest "big" town there were more 10s available (in the form of used G20s and S&Ws) than 357s. In terms of new weapons, for all practical purposes, you are limited to Glock and Sig for the 357 and Glock and EAA for 10mm--not a real significant difference. I guess it's just how you want to spin things, right?
I do know that used S&Ws tend to be hard to find and demand a premium price (and not from collectors), G20s don't stay on the shelves, and the wait for Dan Wessons is ridiculous--somehow, I don't see just a whole lot demand for a $900 357 you have to wait six months or more for delivery. There must be something a 10mm market out there.