Unfortunately SL was just a technology test for Spacetime, AL is the culmination of everything they learned from PL, SL and DL. AL has the most downloads and makes the most money, so it gets the most attention. So just play AL and save yourself the disappointment. But for heaven's sake, don't spend any money on any STS game except AL, or Battle Command.

STS, don't get upset, this is the truth and you know it. I support your games and have played all of them, but now I and my family only play AL, Battle Dragons (cause the kids like it) and Battle Command (because I like it quite a bit).