Which Game to Get...

[panzerde]

The HPS and JTS games are the same games. Tiller has stopped issuing updates for the HPS titles, so if you're going to purchase a game, you'll want to buy from the JTS site to get the most up-to-date versions. If you happen to have or acquire one of the HPS games, you can upgrade it for free to the JTS version by contacting JTS support and showing proof of ownership.

As for everyone playing RBR right now, that's largely because it's the most recently released. In another couple of months it'll be everyone playing Campaign Eylau-Friedland when that one is released. :-)

They're all great. You can pretty easily find opponents for any of them. You're best off to pick a campaign that's of greatest interest to you. I'm sure you'll find someone that's happy to give you a game!