Sandor Clegane has better feats against solitary opponents than Bronn does, holding his own in a brief duel with his brother, and giving Brienne a very hard fight despite debilitated health from a neck infection. By comparison, Bronn hasn't defeated anyone particularly notable, has been challenged by a one-handed Jaime during sparring, was wounded by a sand snek, and had a really hard time with a lone Dothraki screamer. Also recall that Bronn didn't seem confident in his chances against Gregor, and while Sandor isn't as strong as his older brother, he's still strong enough compared to Bronn that the difference won't really matter, and is quicker than Gregor to boot.
Bronn is a very multi-talented fighter, being a very capable swordsman and archer, and is very adept at surviving a battlefield due to his own ingenuity, but Sandor is just the better duelist IMHO.
Were it a battlefield I could see Bronn potentially pulling something similar to what he pulled on the Dothraki on Sandor, but in the Oberyn vs. Mountain arena where both only have one threat to worry about? I can't see Bronn killing Sandor with stealth.
I mean like a situation where Sandor has him dead to rights disarmed on the floor about to lose his head, and Bronn pulls out a knife or secret blade and stabs him in the foot and or throws it at his neck.
Afraid so. Jaime in one of their later spars in season five I believe was managing to hold his own before Bronn grabbed Jaime's golden hand, yanked it off, and smacked him with it. A tactic he would find a little harder to pull off against Sandor.
Sure he did that but he wasn't having trouble at all. He was teaching and therefore was not trying his best. I saw that more as showing Jaime where he was vulnerable rather than him needing to in order to win. If that were the case then Jaime would be around Bronn level in skill and wouldn't need Bronn to slow down that Dorne fighter for him. And Jaime wouldn't need to continue training which he clearly thought he did and that's how Bronn tricked him into seeing his brother
You see Bronn isn't breaking a sweat while Jaime is basically trying his best to keep up. Bronn had Jaime against the ropes when he pulled the hand off. It wasn't a desperation move, it was a teaching moment. That's why he explains the difference between fighting fighting fancy and fighting to win.
Bronn was at the battle of the blackwater although i can't recall if he was around Sandor much but I've heard enough characters comment on it that it must be at least known if not common knowledge; especially hearing the way Baelish tell the story of the Cleganes he made it seem like a commonly told tale