Ronnie would of course win the mass war, but if you want symetry and looks, he wouldnt stand a chance in the 90's against Flex,Shaun,Kevin and he would lose on mass to Dorian ect.
Lets not blame it all on drugs, and as for training, the old school boys overtrained, I know a few people that spend hrs in the gym as if they are on crack but always stay skinny. Todays bodybuilder trains more smart and eats more smart, old school bodybuilders stayed well away from fat even healthy ones. If Arnold got any bigger because of these "new drugs" he wouldnt be that pleasing to look at. When Ronnie was in his early years he never had that big gut and would give Arnold a run for his money on a swimwear competition.
Ronnie would win hands down and if Ronnie was in Arnolds era he would beat him again as he would be smaller and pleasing to look at and yet still bigger than Arnold.
When you have Franco columbo and Ferrigno as your main rival than you dont really have any rivals at all.