The main difference between X and Y is in the indirect addressing modes. You can use X as an index when you are looping through an array of pointers. You can

The main difference between X and Y is in the indirect addressing modes. You can use X as an index when you are looping through an array of pointers. You can use Y as an index when you are looping through an array, where you have a pointer to the beginning of that array. There are also a couple operations that always use X as a source or destination. There’s TXS/TSX, but no TYS/TSY. https://www.masswerk.at/6502/6502_instruction_set.html https://www.masswerk.at/6502/6502_instruction_set.html