Your comparasion of genny to shore power is going to have the problem of time.
Plugged into shore power, you are charging the entire time you are there, the batteries have time for the slow process of topping off the last 25% or so that they can take.
3-5 hours on a genny will not give that long sustained period.
Solar will give you a higher voltage for as long as you have good sun, it wont be 24 hours a day, but there is a good chance it will be 6-8 at the appropriate voltage to get the batteries topped off.
Also solar will charge while you are driving, something the genny or converter wont do with a tt unless your going to run your genny on a rack on the back of the trailer while travelling.
