I've had both, but sold the single believing I'd be able to open the rear of the truck with my trailer attached with the dual swingout. I was wrong and we preferred the single for the following reasons:
- Ease of opening. Each swingarm on these Slee designs is a two-handed/two-step process to open. Pull and hold spring loaded pin, release De-Sta-Co toggles. PITAx2 with the dual. I understand the precaution but have never in 14 years had a toggle open on its own. If they're properly adjusted they never will unless you somehow snag the handle on something. I've seen people weld the hole shut for the closed position or attach a striker plate over it.
- Centered rear tire gives better rearview visibility IMO. I'm less concerned with what's directly behind me on the road than things coming out of the corners of my vision. The dual swingout with a 33" tire blocks passenger rear corner visibility more than single.
- I almost never use the other swingout. We have the gerrycan basket but my wife self severely brained herself on it while we were hitching the trailer, it contacts my trailer nosebox at full articulation, I don't need it for a ladder, and it's not much good for securing other things without losing a whole lot more visibility. If there were a decent way to mount Maxtrax to it I might occasionally use it for that.
- The single swingout worked great for a custom stove table mount I made. The geometry on the larger of the two swingouts doesn't work as well for that purpose.
On the plus side it works ok for hanging solar showers from in camp but then so do tree limbs, roof rack etc.