For the Hot Toys version, the only differences are the accessories. All the figures are the same, right down to their weathering.
HT ESB Snowtrooper: E-11 blaster, backpack, snow base with regular support stand. All you need for an ESB Snowie.
HT Battlefront Snowtrooper: E-11 blaster, backpack, rocket launcher, jetpack, snow base that has a flying support stand for aerial poses. Accessories to make a Battlefront (2015) version. You're better off buying the ESB version if you don't need all those accessories, especially as most folks prefer the regular stand to the flying one.
HT Battlefront Snowtroopers Two Pack: Basically one of each of the above, plus an extra blaster (DLT-20A). Good deal for two figures, though one of the stands is a flight stand.
SSC Snowtrooper: Okay for its time. Exclusive version came with an extra blaster. Some folks have upgraded their SSC with the HT helmet because that was the SSC version’s weakest point, with odd squinty eyes. Still an okay figure. Gloved hands were too big, like oven mitts. Figure body was not the best.
The SSC was $150 when it first came out a couple years ago, went up in price a lot, but came down after the HT version was announced. No real reason to choose it over the HT now. I’ve owned numerous Sideshow Snowtroopers and sold them all. I currently have 4 Hot Toys Snowies. Definitely night and day.
If you only need one and just want the movie look, grab the Hot Toys ESB version. Popcultcha still has all three versions, so you could grab them there. They occasionally have 10% or 20% off sales if you want to risk waiting for a deal.