I personally find GMing to be easier, not least because I have a lot more experience but also because I feel like being a player doesn't give me enough to do without stealing the show. Sticking with a combat example because it is easier, there's two good scenarios from my relatively recent play history.

As GM, the party (with NPC allies) is fighting a group of elite undead warriors bound to protect the entrance to an ancient dwarven crypt. These are semi-intelligent undead.

So during this fight, I'm focusing on managing the undead trying to split the group from each other to be slaughtered in detail, managing direct PM communications with 3 players (the low player count is why there's NPC allies), judging the morale of said NPCs, all while adjucating combat results and providing descriptive text. Plenty to occupy my time.


As player (GURPS game, with a character that dumped almost everything for ludicrous Strength)

I grapple the nearest bandit and rip his head off. Wait for the rest of the party.
I use the head as a throwing weapon to take down another bandit, then jump on the armored car they're using for fire support. Wait for the rest of the party.
Start trying to punch my way into the armored car. Wait for the rest of the party.
Start to succeed in punching my way into the armored car. Wait for the rest of the party.
Surviving enemies are intimidated and surrender.

The roleplaying is fun, but there's just not enough to hold my attention when I'm used to doing so much more.

Out of combat is even worse, because my practiced inclination is to manage everything, so it takes serious effort to hold back and not just dominate the game as a a player.