Ace even burned WB's hand, blocked Aokiji's sneak attack, of course he was going to do that much. But Teach's damages was minimal while Ace almost got his neck broken with 1 punch, he was overpowering him right after he started to take him seriously. Thats why he was asking Ace to join him in the middle of the fight. How many fights did you see someone asking another guy to join him as an underling in the middle of the fight if they are not obviously superior.
Teach used pistols vs WB, and he used metal claw vs Shanks. Low-diff if you consider the fact Teach could use his pistols or metal claw to finish the fight earlier instead using barehands, but choose not to. Then delivered him alive at the end and still didn't kill him despite he could also stole Ace's precious logia DF and give it to Burgess.
Teach used pistols vs WB, and he used metal claw vs Shanks. Low-diff if you consider the fact Teach could use his pistols or metal claw to finish the fight earlier instead using barehands, but choose not to. Then delivered him alive at the end and still didn't kill him despite he could also stole Ace's precious logia DF and give it to Burgess.
About weapons we have no confirmation about how their haki would match, if they had any, so we don't know if he could hurt Ace that way, besides guns and blades in this comic are not as dangerous as in real life, his physical strenght could easily be more threatening. All in all I would say mid diff or a bit higher.