Pb is way heavier. The replacement I got is both noticeably lighter, and more energy dense. It also has a MUCH greater voltage 'band', and higher resistance to damage from over/deep discharge.
The major factor is to to MAKE SURE the LiFePO4 is DESIGNED for a vehicle, at least as well as you can. It would take an electronics lab expert to verify much of the marketing lies, and omissions of many of these kind of products.
The BMS (battery management system) is absolutely key.
(Note-I scuba. A number of products now use lithium power. Many require a BMS. I've seen a some battery pack BMS fail, when the cells were fine.)
A lot of the much cheaper ones you see on Amazon are not designed for a vehicle. I have no idea if they would work for an EV since they don't have to deal with cranking loads. OTOH, the warranties are usually sketchy, and likely the electronics AND used cells are inferior.
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What's not to like?
But is is kind of scary to jump into an entirely new tech. Searching Amazon is an ugly and confusing mess.