I'll say this. Flex had better arms than both of them. When he does a arm shot, the Bi and Tri make a perfect circle. Especially evident back in 1992 and 1993. His Hardbody vid is mind boggling in that respect.... I've never seen anybody whose bis and tris match up perfectly.
That being said, every bodybuilder has a weak bodypart. With Lee Priest, it's his chest, and his huge arms bring attention to that. Ronnie it could be calves, or a lack of exceptional tricep definition. With Flex, it was lack of width and chest.