the speculative comparison between a potential GT rider and a TTer that might turn into one is meaningless since no explicit criterion for GT potential was provided.
for anyone not relying solely on visual perception
it's a no brainer: GTs are all about recovery, ie the ability to do it again tomorrow.
when the cells, glands and nervous system scream NO in the 2nd and 3rd week, there comes a point when no amount of TT power, laser like focus and perfectly aged tubulars can make up for recovery abilities. luckily for lance these skillz could be obtained via syringe.
heck, he was not able to even finish the TDF in 93 & 94. one day races maybe, but GTs no way.