I originally installed MaxAir II's on my vents, bit the two that have fans in them on my trailer have FanTastic fans. The MaxAir covers wouldn't open far enough for the FanTastic fans to operate, as they have a plunger switch on hem to ensue that the vent is open when the fan is running. I changed out the two with the fans for the FanTastic covers,
As for which is "better", I FAR PREFER the mounting method of the FanTastic! If I had realized this at first, I NEVER would have bought the MaxAir's.....