really depends
the 4th die also "post sizes" the case.
so if you're feeding a really tight chamber, the 4th die might be useful to smooth the case so it will fit easily.
if the cartridge chambers easy after the 3rd die, then no, not really.
is it worth it? it's an issue if you have a 3 hole turret, not much of an issue with a 4 or more turret.