The only area that Felder probably has a clear edge is in the clinch with RDA. Felder has really improved that part of his game as he's aged, he's tricky with how he hand fights and is able to land solid strikes even without having much room to work. That's really where he needs to try to get the fight as much as possible.
He can compete at distance with RDA for sure, but I guess I'd still favor RDA slightly there. RDA is better on the mat, especially if he puts Felder on his back.
One thing I'll say is that RDA has seemed to wilt a bit mentally in recent fights. I **think** it's mostly just due to frustration due to lack of ability to keep bigger grapplers off him. That shouldn't be an issue here. But, it does speak to how much "dog" he has in him these days. If it becomes an absolute dogfight and comes down to will, you gotta lean Felder. The way he put it on Hooker down the stretch in that fight (where Felder really should have gotten the decision) showed that he has heart for days.
Felder as a moderate dog I guess seems like the play because you KNOW he's going to absolutely put everything he has into fighting for your money.