No, they are not the same thing. AGM batteries have the electrolyte inside in paste form while regular batteries, whether sealed or not, have liquid electrolyte (sulphuric acid). The liquid can give off hydrogen gas when charging and even bubble out acid if overcharged, AGMs do not. All lead acid batteries self discharge just sitting there, AGMs do this 10x less than wet batteries. AGMs can sustain high current discharge (and charge) better than wet. Of course there is a downside, AGMs cost 2 to 3x as much as lead acid.
Optima is one brand, Concorde Lifeline is another with a little more capacity per pound of weight
or $ of cost. There are other less well known brands as well.
I personally would not want a wet battery in the trailer with me but a sealed wet battery vented to the outside would probably be OK if thats what the budget required.
If you go with a sealed wet battery, do get one with a hose barb that enables a plastic tube to attached that would route any acid discharge overboard.