I would have said the obvious difference is weight. That's the most obvious difference, in my opinion, between the SCAR 17s and any semi 7.62 piston gun. The SCAR is expensive, but so are all of them.
You said your M1A is too "nice" to shoot. Is that due to price? Or just that it's nice? You could buy a second one and keep one nice, if you like the platform.
FWIW, I find the charging handle on the SCAR to be a plus. It's a big plus that it isn't by my face like on an AR. And I like that it operates as a bolt release, forward assist, whatever else you need. I also like that it is reversible, unlike an M1A, AK, etc. But obviously plenty of people do not like that.