I voted for Spring Break as it might be slightly less crowded than Thanksgiving week, although maybe not significantly.
I made this comment on a similar thread talking about how even though August may have lower crowds, I don't think it's worth it due to weather!
I live in Florida - it's so hot right now that it is only kind of tolerable to take a 20 minute evening walk (after the sun has set). Still gonna get sweaty and overheated and any longer is a no. If it rains a lot, it
may be slightly better in the evenings but then you're dealing with rain during the day. I honestly do not know how anyone does a theme park in this weather. Seriously, I cannot fathom how it is fun. You'd have to pay me to get me in a theme park in Florida in the summer. OTOH, a 10/10 crowd day also sounds pretty darn miserable.
If you are willing to spend the money on
Genie+ and to use it effectively (this means a 7am start for someone as well as keeping on top of it during the day), and you are willing to do the very early morning/stay til close thing, crowds can be potentially be manageable. But I would definitely adjust my expectations regarding the eventuality of lines and not being able to do everything in a day.
I personally would probably pick the 10/10 crowds and good weather because even if you have to stand in long lines, at least you're not completely miserable. Whereas in August, even if there are no crowds, you still have to walk around in 95F 3000% humidity. (Honestly, in August, you've still got to do the early start/late night thing just to try to get a break from the heat.)