He's way less physically engaged. He doesn't do the wrecking ball thing and he'll blatantly slow up, reach a little, and let the other team take the puck if it looks like he's going to meet with another player with speed near the boards. That frees him up to make more offensive plays sometimes, because he's doing less plumbing, but there's a ceiling on that for him. His shot isn't good enough and he's beyond awful on the powerplay (he's okay in front of the net, but if he has to handle the puck or make a play, expect a turnover).
He had back issues while he was playing in Europe, but the weird thing is that every once in a while, old Sobotka will show up for a period. He'll throw a couple huge hits and get rough about 50/50 pucks. It makes me wonder if it's sheer motivation instead of age and injuries catching up with him. There were rumors about players on the Blues playing "for the paycheck/lifestyle," and fans have suspected it's him because of the odd inconsistency, but nobody really knows. He's an okay player, he's just underwhelming and redundant on the Blues.