Over the long term, I'd rather have the overhead. The trailers I am looking at, the decks at 18' are all built the same. Their 10k has a pair of 5k axles and weighs 2750. Their 12k sets on a pair of 6k axles that are identical to their 7k axles, except they have a smaller bearing set. Basically their 12k is a derated 14k. The 12k weighs 2850, and their 14k weighs 2870. 20 extra pounds unloaded...
The capacity of the 12k ends up at 9150 and the 14k at 11130.
I won't be towing the tractor often. I'll most commonly move cars or long lumber, but I want the overhead to take the tractor and backhoe someplace if needed. My TLB combo weighs about 8k. I could do it with a 12k easily, but with a 14k only weighing 20 extra pounds and the prices being so close, the 14k is the best route I can take.