Steam: - FPS display - Counts hours - Social achievements - Summer/Winter sales Squad Store: - No automatic updates For some people (myself included), the automatic updates provided by Steam are a benefit. However, most people play KSP with mods. Having the game autoupdate with mods is apparently a recipe for pain and frustration, breaking mods at unexpected times and possibly even trashing saves in the process. My recommendation, having been exposed to both, is to lean toward purchasing directly from Squad. If you purchase from Steam, it's not generally clear that you can launch KSP without Steam, but you can. This can help you mitigate the issues associated with autoupdates.