well no... the master ball i alway use it on a hard catching pokemon (like rayquaza in emerald, or mewtwo in other version) for the rest of the legendery (like the Regi, those damn bird(moltres, zapdos, articuno and also lugia (am i forgeting someone...?)) pkm i use Timer Ball (the longer it take the better) or put them to sleep with paralyze and lower they stats to catch them with a ultra ball, and rare candy.. i never use them i alway sell them lol, it's a stupid idea putting a candy thats can make a pokemon lvl up...