So many things wrong here:
1) First off, Apple doesn't paint a silver color on it's notebooks. It's real aluminum, not cheap-ass paint used by two-bit notebook manufacturers.
2) Are you asking about the electricity each USB port outputs, or the amount of tension the physical port can take? Or are you asking about the scratch resistance of the aluminum?
3) The USB port on the right side of the MBA outputs more power than most notebooks. It is designed this way so that it can run the USB external disc drive (which requires a fair amount of electricity).
4) As long as you're not ripping devices in and out of the port at strange angles, it will not break or warp. It's normal for USB ports on desktops and notebooks to become loose over time, though, even with normal use.
5) The MBA is one of the most structurally sound notebooks on the market. More specifically, if you look closely, the ports are actually embedded behind an aluminum surround. Your USB drive will take more damage than the notebook, however USB ports are notoriously fragile, as they are made out of (mostly) plastic.