But a high cpu use tends to correlate with frame drops. Just to be sure, I repeated my tests and added a dropped frame counter (running test for one minute, the counter ignores the first 10 secs because they are usually terrible):
Preview win32: cpu 35%, dropped frames: 4
Export win32: cpu 33%, dropped frames: 5
Export win64: cpu 41%, dropped frames: 17
So, IMO, win64 wins the "not useful" export competition.