7th gate Lee loses badly. First of all, Gaara can fly, so already Lee is disadvantaged fighting against someone he can't possibly reach because he is outside of his range.
Secondly, Gaara can changed whole landscapes, part 1 Gaara did so I can't even imagine what Part 2 Gaara will do. Lee has nowhere to run, he'll get burried like Kimimaro was, except Lee doesn't have Kimi's ridiculous durability and healing so he gets crushed.
Thirdly, even if Gaara didn't fly for some reason, and didn't bury Lee as well, his main sand is still faster than 7th Gate Lee until we see any seventh gate user dodge Amateresu (Gaara's part 2 sand reacted to and guarded against Amateresu with ease).
I seriously don't see Lee winning this, especially because even if he somehow elluded the super fast sand, he'd still have Gaara's sand armour to get through, and if afternoon tiger from Gai had such a pathetic effect on Kisame, then I don't see it harming Gaara when he's protected by his sand armour.
