Yeah, lead wins hands down. This is a few years out of date now, but when speccing out my system I did a bit of analysis of battery types. We went with OPzS, and so far, so good.
Recycled Lithium Ion is much cheaper still, but more risky (and less maintenance). You'll have to do some pretty fanatic inbound QA to determine whether all your cells are safe to use. but if you do that and fuse your cells individually you should be able to make that work.