Give Arnold the time to train the same way Sly was able to and you might change your tune.
While Arnold's current schedule as Governor is likely hectic to be sure, I believe from the standpoint of conditioning, that Sly would be superior regardless. Back as far as T2, although Arnold looked good, he never displayed crisp condition that Sly is generally known for. I would suggest that a comparison of Arnold from T3 a few years back vs. Stallone of today, would be illustrative of this. Genetically, as far as round muscle bellies and size are concerned, without a doubt Arnold reigns supreme and if in his prime, there would be no contest.