It seems to me that 6700xt is much stronger than 6600. More expensive, too. Personally, I would pay some extra money 6700xt, but it depends on OP’s budget and game preference.
I’d suggest OP to consider several factors:
Is the game you’re playing CPU-intensive? aka Will your 3600X be the bottleneck if you have a powerful GPU?
I had a quick view at this post : https://www.reddit.com/r/radeon/comments/157qa6c/rx_6600_or_rx_6700_xt_for_1080p/
It seems to me that 6700xt is much stronger than 6600. More expensive, too. Personally, I would pay some extra money 6700xt, but it depends on OP’s budget and game preference.
I’d suggest OP to consider several factors: