in the state of Pennylvania, does it matter which party files for divorce?

Because Pennsylvania is a no fault divorce state, the designation of plaintiff or defendant really has no bearing on the outcome of substantive issues.  Rather, the plaintiff is merely the one who filed and the defendant is the one who didn't.  Either party can move the case forward but the plaintiff may be denied alimony pendente lite, alimony pending the litigation  (APL), on an ongoing basis if he or she doesn't try to move the case along.