I think backend is easier because you can write “passable” code and develop a passable architecture and nobody would be any the wiser whereas the Frontend is right in your users faces and it’s a high bar you’re competing with!
The median web frontend is broken in dozens of ways and, when rendered on recent cutting-edge hardware, performs like molasses flowing uphill in the winter. It's seriously difficult for the things your output would be compared to to get any worse.
