Most are a hybrid type battery, which is fine . I think the LifeLine AGM's are true solar deep cycle batteries, but they are more expensive and offer a multi year longer pro-rated warranty.
I use the 12v AGM Deka Intimidator 8A31DTM , never had a problem with them so i just stayed with them and they work well.
I use one inside under the dinette dedicated for the TV , PSW inverter and SAT receiver , that gets charged on a separate smart charger and does need venting. That way my other 2 AGM's (mounted outside on the frame) are dedicated to the fridge, furnace, lighting etc .
doing it this way allows me to bring them up enough (maybe 80% or so) running the Honda gen 2 hrs a day or if the sun is shinning , my 100 watt portable solar does the job.
http://lifelinebatteries.com/LifeLine AGM Deka Intimidator grp 31 at 69# , 5# lighter than the LifeLine.