Snore is definitely out of the question. It is a weak move and only works if you are asleep, which worsens it a lot.
Sleep Talk, however, is different. It is one of the moves used in the very popular move combination ResTalk, which the Pokemon uses Rest and proceeds to repeatedly use Sleep Talk. This is done mostly for Pokemon that have no other way of reliably recovering HP, since it relies heavily on luck and it requires you to predict when your Pokemon wakes up, which also relies on luck.
Sleep Talk is also an okay filler move on some Pokemon if your team lacks a way to deal with common users of moves that cause sleep. It isn't ideal, but it can be useful if you're lucky.
Many Choiced Pokemon are good users of Sleep Talk since they are technically forced to use the move when asleep anyway, but it will really screw you if it wakes up before you expect it to. ResTalk is good mostly on bulky Pokemon that lack a better way to recover HP. Often good moves to pair it with are phasing moves like Whirlwind or status-inducing moves so you can stall out opponents while using Rest to recover any damage received. ResTalk is outclassed by immediate healing moves like Synthesis or Morning Sun as they don't put you to sleep, meaning you don't have to use a moveslot on Sleep Talk. So if the Pokemon can use Synthesis or similar moves, don't use ResTalk.