The reason why the Tekken characters are so good is because their strings still make you guess each time between a high or low. You have a 50% chance of guessing wrong. The SF cast doesn't have anything that is similar to this.
With the nerfs to zoning the SF cast is definitely worse. There are a few characters that I think will eventually lower in the tiers, such as Dudley, due to not having as good footsies. Then you factor in the amazing Tekken AA's and that's a recipe for success. Paul, Law, Jin, and Yoshimitsu all have better AA's than a majority of the SF cast now, lol. Seriously, what the hell? You're more likely to trade with Akuma, for example, then you are with Jin (i.e. you'll never trade with Jin).
SF footsies are also slightly overrated now. Take Rolento, for example. He has outstanding pokes, yes, but he has zero ways to force chip damage now. If you're good at teching you can block low and wait for an alpha counter or reversal opportunity. Ryu was great at footsies but now Akuma is probably the best shoto in that regard. The problem with Akuma's footsies is that they don't lead into any insane setups or strings, just knockdowns. Its not as strong when you consider that you have a 50% chance to escape after each knockdown.
Totally insane. Oh well, Capcom's force-feeding of the Tekken characters has worked for the most part. But yeah, I'm not convinced of the SF cast's strengths notwithstanding a few characters - and I mean few.
I'm willing to debate this if anyone wants. Cheers.