Linares has the frame to eventually move up to lightweight, but Valero is so strongly built at the weight right now. While skills pay the bills, I just worry that Valero's power and Linares' stretches of inactivity would be decisive. I do believe that Linares has better long term prospects, though.
Linares should win. That said even if this fight were to happen, it'd happen no sooner than June 2010 so who knows how much Valero could improve before then.