It wasn't stated anywhere that Lee's cap is the 6th Gate. He should be able to open the 7th Gate by adultery, seeing a how he could open the 6th way back during the War Arc.
Lee probably wins.
Still think Gaara wins even in the movies lee only uses 6 gates nothing more nothing less and if everyone is making g up this immense power charged up lee one could say the same thing about Gaara and his sand control and amount of sand he can control
From what we know about the time skip
Gaara has become a master at taijutsu (was stated in bio) (not on degre of lee but he can defend himself if In close combat cuz his reaction speed was always great )
Has metallic sand which is stronger and faster the. His reg sand but what's good about it is that it's not weak against piercing attacks which is kind of irrelevant cuz lee doesn't have any
Along with just being able to causally block debree off metors etc whereas back in war it took both onooki and Gaara to stop it lee also in 6 gates could bisect a meteor (again I'm just reading from thier bios)
He also has magnet release that strengthens the hell out of his defenses it was stated in the Gaara novel Gaara Hiden: A Sandstorm Mirage
If u don't believe me look it up here's cover page
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Lol I'm a Gaara fanboy to max