I have a 7X14 to carry our two ATVs. It is a tandem axle, and I would not have it any other way. IMO (based purely on my experience), a tandem tows better and is easier to back up.
Braking is not an issue in this state, because the law (MCA 61-9-304) requires brakes on ALL wheels of a trailer of 3000 lbs. GVW or more, and a trailer must have a breakaway system that will hold the brakes applied for at least 15 minutes if the trailer breaks completely away from the towing vehicle.
It is worthy of note that any vehicle being towed in driveaway or towaway operations is exempt from that requirement, IF the combination of vehicles can comply with the provisions of MCA 61-9-312, Braking Performance Requirements.