Hi Tom
Leisure battery is a generic term that covers any kind of battery designed for the living area of a motorhome/campervan/teardrop/caravan/5th wheeler
The usual things that make up a leisure battery are that its;
1. For deep cycling
2. Vented properly to take away any gasses caused by charging/overcharging /or accidental boiling of the battery, this is achieved by having a tube from the top of the battery that is routed to outside of the leisure vehicle (see the battery shown below, I could nt find a picture with the tube in place, look at the left hand Orange battery, the tube fits on in place of the little white bung near the carrying handle)
3. The cell caps are not vented, they are pure screw in stoppers which if you turned the battery upside down would not allow electroyte/acid out.
Surely they have the same in USA? cost in dollar terms $50 ish?
We have discussed this in UK many times and unless you have very specific needs a standard lead acid always beats these fancy batteries, all these fancy battery types usually end up with lower real world performance than a normal lead acid will give.
eg Gel batteries have to be charged at lower voltages, resulting in slower recharge times, AGM and sealed batteries suffer from same constraints ie the reccomended max recharging voltage is 14.4v
The onloy regular advantage is that AGM types will accept more abuse (undercharging, left uncharged etc) but thats like breading an expensive dog that you can kick, without incurring a vet's bill IMHO Stop kicking the dog lol