Q: Is there any point in using a 64th rest or is it better to just say grace note
A: those don't seem like the same thing, but, if you are in a context where you are using 64th notes, then indeed the 64th rest would become relevant. However, there are so many beams and flags on the 64ths, it's not too easy to read, and there's usually no reason not to just switch the tempo and use 16ths or something