Yeah. I think there might also be a tangential aspect here in terms of which is "more enjoyable/rewarding".

There's also the whole "difficult" != "harder", as well. At least in terms of actually knowing what's going to happen, I suppose. A couple people observed (correctly), that the GM has more information, knows what the NPCs are doing, never has to argue with him/herself, etc. So the GM makes a decision and that's what happens. A player make a decision and then has to convince the other yahoos at the table that it's a good idea. Or you get 5 players all doing their own thing, which is also "difficult".

Maybe better to clarify whether we're talking about "harder" in terms of "more work"? On that scale GMing is absolutely "harder". But yeah, if we're talking about some other aspects of play, sometimes being a player can include things that aren't exactly "easy" as well.