First, the straightforward part: these are strictly 12VDC appliances, so when the trailer is plugged into 110VAC, the fan will still be running from 12VDC, and thus either running down the battery
or being supplied by the trailer's AC-to-DC converter, depending on the trailer. Most of our eggs come with a converter, but not everyone uses them.
makes DC power into AC, which is the opposite of the direction needed to supply the fans when AC power is available.
As far as the size and performance of the actual fan is concerned, the Fantastic and Maxx products have about the same specs and look about the same to me. They also both have (at least in some version) multiple speeds, reversing, thermostatic control, and remote control (mine has everything but the remote).
is that while the MaxxFan has an integrated retracting rain hood, the Fantastic Fan has an optional rain sensor, which closes the lid and turns off the fan to avoid getting rain in your trailer. Since I want ventilation on rainy days, the choice of the MaxxFan was obvious for me.
Another difference is that Fantastic Vent offers their fan with a different housing to fit a thin roof better. While that is relevant to most of us, it was less important to me than the rain hood. I assume that there are other installation detail differences as well.