Most marine lithium batteries are LiFePO, not lithium ion. They're far more stable and safe to have on a boat. Compared to lead acid, they have better charge efficiency, deeper cycles, longer lifespans, higher energy density and specific capacity. Furthermore, I've never found lead acid batteries that come close to 1/10th the price...1/4 is more like it.
Fair point on the LiFePO, but none of those other things really matter as they're easily made up for by a larger bank, what matters is the cost per amp/hour and lithium isn't remotely there yet. The exact fraction varies, but lithium isn't going to touch some Costco golf cart batteries at a $100 a pop. You can buy an entire house bank for the cost of 1 lithium LiFePO battery (nearly 1k on Amazon). Unless you just like wasting money, deep-cycle lead-acid is a far better choice.
