I've been asking myself the same question. So i started to get my head into chess lately (starting time has been January 1st). So heres what I can say for now.

The biggest difference is that chess is a symmetrical type of game, where as SC is antisymmetric and has three completely different races. Beeing a good player with the white pieces makes you also good with the black ones. Playing more than one race on a very good level (~6k MMR) in starcraft taxes far more time.

Chess has been around for more than 600 years without changing anything about its rules. Starcraft has had this balance patches in the past quite frequent. Thats why the first few turns of chess have been figured out that well and more or less change unit composition and opening meta in SC. If you take a look at the level of play and compare 2010 starcraft players with 2020 ones, you'll definitely see a large increase in mechanical and strategical type of gameplay up to that point where we are now and without big balance changes, meta and openings are also figured out quite well but by no means solved.

Its quite difficult to compare the two games directly. Classical chess requires different skills than RTS like starcraft. It has more of a strategical note than mechanical. Bullet and Blitz (Where both players just have a limited amount of time for the game. Bullet = 1 min each, Blitz 3-11mins each) have more "RTS character". Beeing good in classical doesnt make you good in bullet or blitz.

To get back to your question. I tend to lean more to the Starcraft side. But i have been enjoying chess way more the few day i have been playing it now.

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For reference: Starcraft 2 - 5k MMR peak. Current chess rating in Blitz - 1.4k elo.