I have a single axle trailer, because they do not make a dual for such a small trailer (which is 15 feet long, coupler to rear bumper). But I would prefer a dual. Not just for the smoother ride, but for safety. If you have a blowout on a dual, you will be able to keep control of the trailer. On a single axle, it is not so easy.
So bottom line, if you can find a dual axle in the length you want, I would get it. Yes, you will sacrifice some storage space (because the wheel wells stick up into the cabinetry). And yes, you will have to buy an extra set of tires. Well worth it, I think.
2012 Fun Finder X-139 "Boondock Style" (axle-flipped and extra insulation)
2013 Toyota Tacoma Off-Road (semi-beefy tires and components)
Our trips -- pix and textAbout our trailer"A journey of a thousand miles begins with a single list."