I wouldn't go dually unless you plan on towing a monster 5er. If you plan on keeping the weight under 14,500lbs, which is easy to do - I'm at 12,800lbs and 35 feet and definitely don't need a dually.
If you want to go to 16,000lbs or possibly more, then yes a dually is the best choice. If you don't need duals, don't buy one. PITA to park, rougher ride and may not fit in places you want to go. JMO but it's probably overkill unless you plan to go big.
2013 CrossRoads Cruiser Patriot CF345RF
2011 Ford F350 Lariat FX4 CC 6.7L Turbo Diesel (Heavily Modified)