Arm is better because there are more than three companies who can design and manufacture one.

Edit: And only one of the three x86 manufacturers are worth a damn, and it ain't Intel.

Edit2: On further checking, VIA sold its CPU design division (Centaur) to Intel in 2021. VIA now makes things like SBCs, some with Intel, some ARM. So there's only two x86 manufacturers around anymore.