tried the demo for the past few days. A couple of comments:
man, they REALLY abstracted the planet management part... too simple to my taste, after experiencing how fun planetary management can be in GC2... once you colonize a planet, nothing much need to be done for it other than tweak one or two sliders as necessary.
There is no intrinsic motivation to colonize planets, because the real meat is in the tactical combats. Planets only serve as convenient star port and refueling post for most of the time.
Also, after we're done terraforming the planet, there's nothing much left to be done on the planet, and terraforming process can finish quite early.
There's no character there in individual planets, something that would drive me to love or hate specific planets other than for statistical reasons... whereas in GC2 there are various reasons to salivate over an enemy planet, and to hold dearly to your own... and GC2's graphical representation and descriptions of planetary details and improvement, with their tie-in with technological researches and such, really lend a lot more character and fleshing out of the planetary management process...
HOWEVER, their tactical combat aspects are very intriguing... very well fleshed out, with lots of different viable tactics towards warfare and invasions... it's not just a matter of rock-paper-scissors... a lot of factors influence victory in combat, even situational factors such as turret emplacement and ship positioning, ship formations, relative velocities, asteroid hazard during combat, tractor beams, poly-accurate targetting, cloaking & countermeasures, mines warfare, exotic weapons with special qualitative effects instead of just having a big plus to its damage rating...
GC2 does a better job at keeping the spreadsheet aspects clean, manageable & accessible. It's harder for me to manage my ships in SotS once i have whole flotillas of em running around the galaxy. It's hard for me to access planet information out of the many other planets i've colonized. Economical tweaking is more refined and easier process in GC2 where we have all handy data in one place while we're tweaking (the F4 screen). It's easier to see which planet's building what in GC2... the F6 colony list is very powerful and handy... it's easier to navigate thru planets and ships in GC2...
on the other hand, SotS has an excellent Updates Announcement System that pops up at the beginning of each new turn... they're comprehensive enough for me to sufficiently run my turn-by-turn affairs by flipping thru them and taking care of things one by one... Whereas GC2's announcement popups are rarer... I originally thought it is sufficient enough, but nevertheless I still have to scour all over the galaxy from time to time to check for errant ships or planets...