Is the AR less desirable because of the fittings? In a word, yes.
While I think the 390SS is a well-designed machine and it seems very stout, I'm thinking of selling mine off after only a few uses. First, I'm not a big fan of the plastic outer case (on ANY of the current electrics that have a case), and the hose reel -- perhaps because of the case -- is necessarily mounted a bit too high, causing the unit to be tippy when you come to the end of the ~20 foot hose while working around a car. The hose itself seems to be pretty good and it unwinds easily enough but it has crazy memory and constantly re-loops and gets tangled on itself, reducing its effective length while in use. Electrics are easy to move around so I don't need a 50 foot hose, but 25 would be nice, especially if it stayed straight.
At this point I'm thinking of selling it for half what I paid and eating the rest, and getting the GreenWorks 2000 from Lowes. The GreenWorks trades a plastic case for a simple steel frame like most gas units have, with the pump down low and the reel directly above. The hose looks similar to that on the AR, but with M22 fittings at either end, allowing me to get a better, more flexible PU hose like a Flexzilla. I thought I did my homework but I didn't realize the AR's hose would tick me off so much, and because of the connectors it can't be swapped for something better.