I have a single axle 16’ I’ve pulled for over 20 years, no problems at all. It is very sensitive to steering input so many people feel it’s hard to back up. But I take it in some very tight places and the sensitivity and maneuverability is an advantage to me so I think it’s easier to back.
When I first bought it I was concerned about losing control of it if I blew a tire and that was the first question I asked on the forum. The responses were overwhelmingly that was not a concern. Being small and light, 3000# loaded, I also don’t need to bother with WD and sway control which I like.
I’m not sure at what length and weight I’d lean toward dual axles. But the need for WD and sway might be a factor.