I'm going with Lisa myself, mainly because she had more time and didn't know she could go up from the Tomb. Tia knew the Observatory was there and a path upward existed, whereas Lisa didn't seem to know.
What's more, neither player made any progress, but the reason I think people tend to overlook Lisa is because Steve made much progress toward the artifact than did Jon (and maybe Steve made the Alhambra team look better than they turned out to be).