Tandem axle will provide a much more stable towing experience. Less potential for sway, and in the event of a sudden blow out, there is the second tire to support the trailer until you can safely get somewhere. Tandem axle will also distribute the weight of the camper over 2 axles instead of one, which means less stress on each axle, a smoother ride for the camper, and the potential for the camper to weigh more, as the weight is distributed to 4 tires instead of 2.
All of these are minuses for a single axle.
The disadvantage of a tandem axle is the pivot response of trailer. The tires do not pivot like a single axle. There is always some side force on the tires. On one side of the trailer, one tire sidewall can be forced inward, the other tire forced outward, especially noticeable when backing a sharp turn. This never occurs on a single axle as there is only 1 pivot tire. This is about the only advantage I see with a single axle trailer.
Dealers: Before purchasing, check with your (local) dealerships to see if they do warranty work for the your brand not purchased there or a brand they do not market. However, if you are paying the bill out of your own pocket, most RV dealership-repair shops will fix anything, pretty much. They are there to be in business, not turn potential customer money away. They'll fix if you pay, warranty or not. You pay, they won't turn you down. Then... if you need to haggle with your manufacturer .... that's up to you. Bottom line, check with your local shop to see how they handle warranty work on a camper they don't sell. And if willing to pay cash yourself, you'll have no problems 99% of the time. (provided they can get the parts needed for the repair knocks out the other 1%.)
No experience with either brand of camper you're considering. But, use your best instincts and your own "gut reaction". This is usually the best indicator.
