I think the flavor difference between 40 and 50 and then again between 50 and 60 are going to be so slight that few would be able to pick it out. The difference between 40 to 60 will be more pronounced and many more will notice. All this means is that your beer will have a less layered flavor profile, a bit more one dimensional (at least on the crystal contributions)--somewhere between the two, without the differences each offers. Other than that get a touch less color from it, as unionrdr said.