Lithium batteries have a much longer lifespan than lead acid, which would eliminate the need to replace UPS batteries every few years. They are also more power

Lithium batteries have a much longer lifespan than lead acid, which would eliminate the need to replace UPS batteries every few years. They are also more power dense, so if the goal is just to keep a machine running long enough for a clean shutdown, you can get away with a smaller (energy and size) battery for the same load.