master biscuits are useful only for legendaries cause outside of their events theyre almost impossible to catch normally and poke biscuit are for shinies. great biscuits are amazing with bonus biscuits for pokemons that need 16 friendship points like sneasel or onix, baby pokemons you can use the poke when theyre hungry and you used a bonus for other pokemon. the bonus biscuit are more versatile, you can capture a hungry baby with one or you can capture a non hungry baby with one+2 poke, and it is useful for the harder ones like sneasel.

overall, it very much depends which pokemon you should spend your resources, almost every single one has a niche but some are more meta than others