If all else is really equal, then the two arm swing should be easier, but often all else isn't the same.
Two arm swings should be less taxing to the grip and forearms per rep and unit of rest. But two arm swings are often done for more reps at a time (because you can), with a heavier bell (because you can), with a more powerful hike pass and hip drive (because you can), and/or with less rest than one arm swings, so the grip fatigue accumulates.
The rest equation can be sneaky. As an example, say you are doing sets of 10 on the minute, alternating arms. With one arm swings, each set might be more taxing on the grip, but you have two rest intervals and a work interval to recover (about 2 minutes, in this example). With two arm swings, you only have one rest interval to recover (not much more than 40 seconds, in this example).
The snatch is more taxing to the grip due to the increased height of the drop, and the more vertical bell path.