The first rule of buying a trailer is whatever you buy will eventually be too small...
If you're only going to tow the Pioneer, most any light duty trailer will work. The problem is that once you have a trailer, you find all kinds of things you need to haul. You didn't say what you're going to tow with, but that really sets the bar as to what trailer to consider.
As others have said, one advantage to a tandem is you can have a flat and it probably isn't going to be catastrophic. A problem on a single axle tire at highway speeds with a 1 ton+ load could be exciting.
We've got four trailers:
- 18' Dovetail Flatbed w/ Tandem 3500# Axles
- 18' Enclosed w/ Tandem 3500# Axles
- 20' Enclosed w/ Tandem 5200# Axles
- 14' Dump Trailer w/ Tandem 7000# Axels
I use Vulcan tire straps to hold the Pioneer down. They lock onto the D Rings on the floor of the 20' enclosed and the dump trailers. Once you figure them out, they go on quick and hold tight. https://amazon.com/gp/product/B0714FZ7VN/?tag=sxsweb24-20
The first three trailers were used to move our FL homestead to our WV farm over a total of 9 trips, 1900 miles roundtrip. (Technically we have a fifth trailer, a 48' dry van with a 4400# liftgate, that was used in the move. I paid a trucker from FL to bring it up and then paid a local trucker to bring it the mile down our narrow, winding road.)
The most limiting factor when buying a trailer is the tow vehicle. Our Toyota Tundra has the factory tow package, a quality brake controller, and air bags. It weighs around 6400# and it's max tow capacity is spec'd around 10,500#- about the max GVWR of the 20' enclosed trailer.
While 10,500# sounds like a lot of capacity, you lose about 4000# due to the trailer's weight. If you're moving heavy stuff, it's very easy to exceed 6500# in 20'.
The 18' enclosed trailer only made one trip, containing stuff we wouldn't need for a while, as it's cargo capacity is only around 4600#. We bought the 20' trailer to use as the primary move trailer since it had 5200# axles.
Even with the added weight capacity, the 20' trailer was probably well over 10,500# on a couple trips. I bent axles on two trips where it was loaded heavy and I hit potholes I couldn't avoid on the Interstate in SC. (SC has the absolute WORST highways of FL, GA, NC, VA, and even WV.)
On a side note, it's actually pretty easy to straighten a trailer axle with a logging chain and a hydraulic ram... (Plenty of YouTube videos, including one from a truck shop in Central FL that uses lasers and a computer to do it for RVs and trailers.)
I put new tires on the 18' enclosed and the 18' flatbed before bringing them up. It was cheap insurance to minimize the chance of a blowout.
All of the trailers have electric brakes. When putting the new tires on the flatbed, I discovered it only had brakes on the front axle and the rear axle couldn't have them added easily. It turns out this is VERY common on tandem flatbeds with 3500# axles. It's not a huge problem unless you're hauling a lot of weight. Especially when the towed weight exceeds the towing vehicle weight, brakes are important to keep the trailer from shoving the tow vehicle during slowing or stopping. Learning how to set the brake controller for a given trailer, given cargo, and road conditions is a critical skill. Even more important is learning how to load a trailer for proper tongue weight.