Extremely light weight! For example a typical 16 amp/hour battery weighs 5kg. A replacement Ultrabatt Lithium battery weighs an amazing 860 grams complete with the built in Battery Management System.
Very high cranking power relative to size and weight.
Very low self-discharge rate (about 3% every month).
Very small size.
No internal liquids or acids that can spill - can be mounted in any orientation.
Unlike lead acid batteries LiFePO4 lithiium batteries do not produce explosive gasses like hydrogen when charging or discharging.
Very fast charging times typically a discharged battery can be fully recharged in 1-2 hours. By comparison a discharged lead acid battery will take over 12 hours to charge to full capacity.
Vastly superior reliability and a very long service life compared to lead acid batteries. Target life for lithium motorcycle battery (With a built in BMS) is ten years!
Lower per year cost of ownership than legacy lead acid batteries.