Supposedly, PCB has a rank system, but any changes in difficulty are so minuscule as to be considered completely negligible, with one exception: Lyrica's opener (don't know if the other Sister's openers are affected too, since I never play anyone but MarisaA). As I mentioned, the only difference seems to be the purple arrows getting mirrored. It does change the way you need to approach the attack, but I think all you need to do is make sure you slip through the purple arrows before you do the same with the red/brown ones - essentially, don't try to dodge both waves at the same time. Needs testing, of course, but that's my take on it.