For Hardi siding I always use my framing nailer with a plastic foot. Works well, I just set the nail depth with an air regulator.
Roofing takes a different coil nailer than siding so you will need at least two guns.
For home use I look through the pawn shops and buy something that doesn't look completely beat to hell and functions properly when I test it. Hitachi, Senco, and Bostich (which also seem to get rebranded as Dewalt or PC as well) are most common pro gun names and everyone has a favorite out of those 3 names.