4x4x4 has parity problems, same as 5x5x5, but as the GP posted, the number of parity cases for 4x4x4 is higher, which makes it slightly more difficult. (I prefe

4x4x4 has parity problems, same as 5x5x5, but as the GP posted, the number of parity cases for 4x4x4 is higher, which makes it slightly more difficult. (I prefer solving the 5x5x5 for exactly the same reason).