Both monsters.
Posting random pictures, however, simply distorts any meaningful comparison.
From the front, Nasser wins, maybe, just. 'Relaxed', from the front he looks markedly better than Dorian. When you talk about mandatory poses, Dorian makes up for the deficit in all but the side chest and front double bi. Also, consider, and anyone who saw Dorian on stage would agree, that there is a quality to Dorian's muscle beyond simply 'conditioning' which owned all others. Also consider that Dorian's torso length is ideal and that Nasser's is a little on the long side - (conversely, Ronnie's torso is on the short side) which does impact on overall aesthetics. Head to toe, from the back, Dorian owns any other bodybuilder in history, Ronnie included, and convincingly.
Prime Nasser was phenomenal but cannot quite match Dorian.