I'm very happy with my Viair 400 RV, but I got it 3 years ago for a major discount. I have no idea why they temporarily dropped the price as much as they did at the time. I might be willing to pay the current price. Not sure. I'd have to assess other options before deciding.
I chose a 12V system because my truck will always be with me to power it, but I won't always have a source of AC power. Others will give their reasons for their choices.
The "RV" designation means it comes with an extension hose. The pump has to connect directly to the battery due to power demand. That puts it at the front of your vehicle. The extension hose lets you get to the back axle of the trailer.