There is no doubt the games are different and have different play styles. It is also not up for debate that MKx is a hyper aggressive game relying on pressure play and SF has always been a much more defensive style game relying to footsies and such. It is also imo, not arguable that Sonic defiantly seams to exhibit tendencies that are typical NRS play with his FANG games, that of heavy pressure. Also, imo, this will always result in heavy punishes in the long run.
That being said, getting 10th or whatever it was in Top16 in his first SFV Major is a fantastic start. There is plenty of time for the nuances of SF to be learnt and I am confident that if he wants to learn it he can. It is kinda ridiculous to expect a guy that has spent years playing hyper aggressive games to suddenly play in a completely different way. Even so, he did very well and I expect this is the only beginning. He may even be able to find some kind of middle ground between the hyper aggression play and tactical SF play that is unique and enable even more wins.. who knows.
All I know that the game is like 2 weeks old, and if I got top 10 in a major in that time I would be fucking happy as muck but arguing over Sonic as a player seams silly as he is obviously a great player, and using this top 10 win as an example of him sucking is ridiculous, and also saying that he is going to crush SFV is ridiculous. People are not lying when they say that WB wasn't the most heavy competition (yes there were some greats for sure), but it wasn't even a official part of the capcom pro tour.
Personally I am in Sonic's corner here and I believe that if he enjoys his time playing he can be top tier in the US at least. I also think that some major adjustment in play style will have to happen, well at least I think so. Either way I am very VERY keen to see where he goes and I'll be tuning into his games 4 sure.