Doors and Windows - vinyl or aluminum clad dbl hung?

In new construction in mtns of NC area, what is the best choice for double hung windows; vinyl clad or aluminum clad? And double pane with argon filled also? Do I also need low E? Would the same hold true for sliding doors, fixed glass and casements, as I'm having all these types?

I would opt for the vinyls. Compare them by comparing their warranties. A $500 window with a 5 year warranty is not nearly as good a deal as a $700 window with a transferable lifetime warranty. Low-e glass for sure, and argon only after comparing the festation ratings of low-e with and without it. The additional savings realized with the argon might not be enough to justify the additional expense. Use the low-e in EVERY window, regardless of it's frame configuration (sgl/dbl hung, picture, casement, whatever).