I do not think you can get a RV size AGM for under 100 and never could 300 perhaps but never 100.
The batteries under 100 are GC-2 Flooded wet cells from Sam's or Costco and if I were to replace my batteries that's what I would get You need two, in series to get 12 volt.
I've used Flooded wet GC-2's, Maintenance Free and AGM. They were all good when new but the AGM's died first, then the MF's and finally the Flooded Wet GC-2.
However if access to the batteries for the purpose of cleaning and adding distilled water (To a level 1/4" to 1/8" inch below bottom of filler tube) then AGM might be worth the added cost.