I use AF only.
#1 reason is that I can winterize at the storage yard (don't have to bring camper home) only having to bring my battery. Bring the battery and LP tanks home, and I'm done. But of course, de-winterizing with AF is a process, versus nothing really to do if you only blow out with air.
To a lesser degree, I like knowing that I have removed every bit of water from the lines. It's possible for air to shoot across the top of water at a low point in the hose, leaving. There are techniques for minimizing this risk (hitting with air multiple times, etc), and I know that a small amount may not be enough to rupture a hose.
The time to run AF or to blow with air is about the same.
IMO, if you are going to run AF, blowing out with air first is a complete waste of time and energy.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller