Hard Reset vs Clear Storage

[donc13]

Verizon vs6900, got it new from Verizon about 3 weeks ago.

A couple of things, what's the difference between a hard reset, and clear storage?

Second, there are several .cab files in /windows such as the one to add opera, etc. There's also a radio refurbish cab there. If I stop customizations from running (after a clear storage), which of these cabs are safe to run, and yet still be able to use the GPS (with Vahalla Legends) with everything else stock?

ROM 3.14.605.1
Radio 3.37.78