This is perhaps one of the most even match ups in a long time. I could see this going either way.
Advantages for Franklin: Conditioning, Ace does not gas, ever. Striking, while Hendo may be more powerful, Franklin has more technical striking ability by a mile.
Advantages for Hendo: Power, hes got bricks for hands. Chin/toughness, the dude can take a beating like a man. Wrestling, he can take down and control Ace, but I dont think he'll do much damage on the GnP.
I would consider Franklin to be the faster of the two. If this fight goes for three rounds, Franklin by UD, but either one of them has the capability to knock out or TKO the other.
But if all else fails