Jones is more faded. The only way you can really tell is by how they fared against the world class opponents. Jones hasn't beaten a ranked fighter in 5 years (anyone who tells you that Ajamu, Hanshaw, or the Trinidad who unretired for the 2nd time were world class fighters is lying), and has since been KTFO twice. Casa, while clearly faded, still has his main assets. He's still crafty, still knows all the dirty tactics, and is still slick even though he is more hittable now. He knocked out Katsidis in his last fight, and Katsidis is a world class fighter at 135lbs, plus about 2 years ago he beat Corralles. Casa is past his best and over the hill, Jones is shot.
Casamayor, no question. The problem with Roy Jones is his confidence, physically he's still pretty sharp.
Roys legs and stamina are more shot then anything on Casamayor but I still believe Roy has boxings fastest hands so this is strange.
RJ was struggling against Tony Hanshaw and had to adopt a turtle shell defense against a former welter champion who is past it himself. Casa still shows very good movement and still has a fast explosive left hand. He actually climbed back into the ring after a hard kd to ko a lightweight champion and was considered shot even before he beat Chico a couple of yeras ago.
Casamayor's skills haven't regressed that much. RJJ's has...That said, his current skills may be enough to beat the likes of joe calzaghe