If you don't have any obvious problem, why do wanna switch right now? Memcached or redis are probably better but if you don't need them right now, it is better to leave them. As long as your caching strategy is sound and cache interface is abstracted you should be able to add them later when you actually feel the need to switch to a scalable cache.
Also xCache in PHP is an opcoder cache.. Memcache & redis are more or less like a out of proc key Value pair.. If your site is running on 2 or 3 server and you need the context b.w them shared not just kept individual instances, those caches will help.