You want the higher AH 6s. Eg Trojan makes a 210 and a 225. Choose the higher AH option.
Not sure of qualities. it is more about taking proper care of them. I am very happy with my 230AH East Penn GC15s, but there are many other choices.
You do not fully recharge batteries while away on generator. You run them down to about 50% and then recharge to 80% or so (called "50-80s") it takes too long to get them to a higher SOC on gen time. Wait till you have shore power to get them to full.
If you have solar you can get them to a higher SOC before dark. In that case, do your 50-80 in the morning and let the solar do what it can the rest of the day. (you can run the solar while doing your gen/charger to get more amps--just leave the solar on all day--it will do whatever it can.
The time to recharge two or four 6s from 50% depends on your charging amps and whether you do a 50-80 or a 50-90. The 80-90 part will take an extra hour of gen time for not that much gain. Think of three hours of gen time for a 50-80 on two 6s with a 55 amp charger, eg.
You need enough generator to run a charger at higher amps. two 6s can take 80 or so amps at first and four 6s can take twice that. Some inverter gens have 150a chargers, but that takes a 3000w gen to run it at those high charging amps.
Sounds like you could sell the 2200 and take the 3100 as your portable gen or VV depending on ? You don't need both anyway.
