This will certainly depend on what you are intending to use your trailer for and how much carrying capacity you need to get out of your enclosed trailer. The single axle option is going to be an excellent choice for hauling smaller equipment such as a push mower, hedge trimmers, hoses, bags of mulch, and other smaller items. The mobility is great and can be towed with a wider variety of vehicles, but with 2,300-pound payload capacity, you may be limited in your carrying options.
The tandem axle option for the 6X12 enclosed trailer boasts almost double the payload capacity at 5,200 pounds and will allow you to haul much heavier equipment. The tandem axle option also includes an individual braking system in each axle to help ensure the additional weight can stop safely. While it mainly depends on your needs, Renown has the available options to make your trailer completely the way you need it.