Definitely Joseph:
While Deku has the AP and a much higher attack with 20%, Joseph does indeed have a small chaining scale (Post-training Joseph = The 3 Pillarmen > Santana > Dio) and on top of that, he has hamon, which can not only bypass durability to an extent but can be used in multiple ways, such as some level of mind-control, forcefields, etcetera.
Joseph is alosa tactical genius: even if I am not very knowledgeable on Midoriya, while he seems a skilled fighter, his strategies and fighting style are things that Jojo can quickly understand and adapt to, and eventually overcome.
And if the worst happens, Jojo can probably pull something out of his arse, like weapons or tools which , other than making Midoriya question what the hell is going on, can overcome some advantages that the guy may have, such as range or AP to some extent. I mean, he's in the middle of Central Park, he's gonna find something.
When Derku is going to decide to use 20%, I don't think that it's going to overwhelm Joseph to such an extent, especially if it damages the body. And Let's be honest, if it's only an Ap boost, I doubt that Joseph wouldn't be able to get around it in a way or another.
So yes, Joseph for those reasons.
