Both of these classes have one different prerequisite. So whichever class I would take I would have to take the prereq for that class too. The pre req for Complex Variables is Calculus of Several Variables, and the pre req for PDE is Intermediate Differential Equations (ODE 2?). Here are the discriptions of those classes:
Calculus of Several Variables:
Differential and integral calculus of functions of several variables, vector anylasis, Stokes' Theorem, Green's Theorem and applications.
Intermediate Differential Equations:
Systems of differential equations, series, solutions, special functions, elementary partrial differential equations, Sturm-Liouville problems, stability and applications.