They are all great. But that picture of Flex says it all. For all around perfection and detail. Flex has or had the most perfect arms. the detail is just out of this world.
Great arms, right up there and should've won at least one Olympia in fair contests. Comparable but not better than Robinson, Dillet, Coleman, Schwarzenegger, Fox, Oliva, etc.
That pic's not any more special than any number of others. If you look at Coleman & Wheeler side by side in the late 90s, Wheeler looks incredible yet Coleman still had more arm size, better peaks and more refinement/detail.