Kris, I see it (syrtis major) as more rounded if the seeing is very good. I think I sketch the darkest albedo features only and I don't shade them off like I should. I'm still struggling with my Mars sketching.
i think it's something inherent to us sketchers to be (too?) critical about our own technique, or the final result of a sketch? it's never the way we really remember seeing it at the eyepiece, but it's so difficult to do that with pencils. i guess Photoshop and the likes are most suited to render the most realistic image (as oleg's sketch) but i'd like to keep at the pencils & paper
i feel i'm still struggling too at mars sketching, trying to get the colours right for two oppositions now!