The 2010s2 is the newest and current version. I don't see much information on changes in the newer one beyond using relays for input switching, instead of simple mechanical switches.

I think aluminum case is new, and guessing that there might have been circuit board layout, and maybe some component differences.

Does the new version sound noticeably better? I don't know, but I tend to go with newer versions in the hope that they are an improvement.