Flex would defeat Lee, basically due to being better overall from the rear, especially condition wise, lee always struggled to dial in hammies and glutes and his lower back to a lesser extent.
Lee has better double biceps, from front but torso issues in other poses make front comparisons a lot closer than rear.
From the side their even upstairs but leg wise flex hammies superior again.
Lee is tier 3. I'm not sure Flex is.
$2000 and under (tier 3)
Arntz, Efferding, D. Riley, Constantinos, R. Burneika, Centopani, S. Milne, S. Farmer, L. Priest