Why not dual boot? It will give the best of both worlds then and save your bacon if one OS is crippled by something you do. Even set up an OS for gameplay only - I have done that with 98SE for grahics work (photoshop and video editing) and all the excess stuff is removed.
I don't use XP - but am very happy with Win2k. For stability, it seems that XP is excellent, but I don't know about gameplay.