Great matchup! I actually prefer Beatty in The Parallax View because of the time and atmosphere - the 1970s were well into the poltical-thriller genre that the 1960s had only really touched upon - JFK hadn´t been assassinated at that point and there was still a certain element of naivety with the general public albeit the Cold war paranoia was abound. Another great, often-forgotten movie of this conspiracy-type if Executive Action from 1973 starring Burt Lancaster:
I prefer Parallax View also. It's a cerebral and poignant political thriller and they damn sure don't make those anymore. Everything is mindless now. Never seen Executive Action. Will add it to my list.