If price is no object, Lithium Ion batteries (and presumably a matching converter/charger) would be the nicest generally available today.
For most of the rest of us, 6V golf cart batteries probably offer the best bang for the buck. Two or four of them would do quite well for this sort of use. I have a pair of them in my class C motorhome, and in nice weather I can go several days, maybe a week, before I have to charge them with a little bit of electrical conservation. I don't know exactly how long because I haven't been in one place dry camping for that long yet. (It's closer to two or three days if I need to use the furnace some at night, depending largely on how much the furnace gets used.)