Mark,
A key spec you'll need to be concerned with is wattage. From all the input below, sounds like you'll need 3500 to 4000 watts of gen to power your trailer, including your AC. I've read that twinning 2 Honda EU2000i gens does not yield a full doubling of wattage but still enough to start and power a 15k BTU AC.
If it's in your budget, strongly consider the inverter style generator. It produces a true, not modified sine wave output. Some equipment requires true sine wave AC power. This way, no worries. The Honda EU series as well as some of the Yamaha's and probably others are true sine wave, inverter style units.
Consider the noise level. Most units are rated in dB. When comparing, be sure to look for what load the sound pressure level measurement was taken at as well as the distance it was measured from - then make sure the others you are comparing were measured in a similar fashion.
Consider the size and weight of various gens. Two Honda EU2000i units are easy to transport by 1 man and to store. The next larger units from Honda, Yamaha and others are much larger and heavier and sometimes require 2 people to lift them. All depends on what your storage/transport options are for your gen(s).
Consider non-RVing uses for your gen. When else would/could you use it and what gen would be best for these other uses.
You have a TT so a built-in is less of an option but for others reading this with 5th wheel trailers, a built-in unit is another consideration.
Have fun.
Jim