Im taking Jones UD. I just dont think that Spinks would have a answer for Roys speed and athletism. Has there ever been faster hands at the light heavyweight division?
Spinks is my pick... he's got a lot of tools to deal with Jones' speed. While Jones was a huge puncher at 160/168, at 175 it was still very good, but Spinks has a good chin. The other way around however, i wouldn't say Jones has a glass chin at 175, but it was certainly less reliable than Spinks', and Spinks could punch! Spinks didn't have Jones' sick speed but he did have a great technical foundation, he's 4 inches taller and he has something that Jones lacks: a good jab. This would be a close one, but i'd pick Spinks to win 2 out of 3.
Have to go with Spinks. He was a better fighter. Jones would cause problems for anyone but he's not in Spinks' class at this weight.