I just came across this GREAT rant on solar and batteries. It is by a guy in the US who full-times in a big RV there. He makes a LOT of sense in his post. It is pretty long, but very much well worth a read:
In short, he is advocating Trojan T-105 batteries. He is tending towards a smaller battery bank than you might think, but better charging regime. He is saying that T-105s could do with being charged at 14.8v rather then the generally accepted 14.4v used for most batteries. This actually gets a lot more out of a solar panel, as they generally run at a higher voltage anyway. Adding more batteries to a system (or more solar panels) without getting the charge voltage right and the wiring right is wasting a lot of power.