45W for reversing lights is WAY over the top, but he quoted 25W which will be more than bright enough.
Xenon and HID are the same thing I think, Xenon is the name of the gas inside an HID bulb. Some filament bulbs advertise themselves as being Xenon, but infact they only have something like 13% Xenon and the rest is still Halogen, but it makes them a tiny bit brighter/whiter, but they are still nowhere near as good as proper HIDs.