I go with Lyle, simply because Lyle always showed up in good condition. With Mercer you just never knew what kind of a performance you would get. Lyle was really a good fight, had his limitations, but a really good fighter.
I think Lyle had more proven boxing ability over the distance and won a lot more decisions against quality fighters... Of course, the prospect of Mercer scoring a knockout is possible, but Lyle was a man who rose off the canvas to KO Earnie Shavers, plus traded life and death against George Foreman with a fair amount of early success.. Mercer can certainly crack, but not on the level of either of those other two guys.. I'm going with Lyle via close decision..
Lyle fought the better competition, however slight, so I think Ron takes a close majority decison over Ray.
If the two were both at their respective peaks I would give the edge to Lyle. I think he outworks Mercer for a UD.
If Lyle boxes, as I know he can do, he wins a decision. If he wars with Mercer, he probably gets stopped.