I don't think that the advantages offered by Lithium-Ion outweigh the disadvantages (high cost, not always a straight swap for the OEM installation, difficult and expensive to keep them trickle-charged in the off season, etc.)

I've got two motorcycles to take care of - a Honda ST 1100 that I keep in Europe and use only occasionally, and a ST 1300 home in Canada that is used in the summer months.

I buy plain old-fashioned OEM-spec Yuasa lead-acid batteries for both of them. Yuasa is the high-end brand of lead-acid, they are reliable and last about 4 to 5 years. All good quality lead-acid batteries nowadays are "sealed units", meaning, the acid is already inside them when they ship from the factory, it stays there for the life of the battery and there is no provision (or need) to ever add water to them.

AGM (Absorbed Glass Mat) batteries are just a variation on the lead-acid theme. Same with gel. If you buy a high quality wet-cell battery, it won't spill or leak if you drop the bike (unless the battery is physically damaged, which is a whole different issue altogether... physically damage a lithium-ion and you get a fire).

Lithium-Ion batteries offer greater capacity in a smaller package, which translates to less weight, but honest to goodness, I don't think that saving a few pounds of battery weight is worth the significant price difference and the additional cost of buying specialized trickle-charging equipment.

I had to specify a battery to be fitted as standard equipment in a 19 passenger aircraft that went into production 10 years ago. I spent a lot of time evaluating lead-acid vs. nickle-cadmium vs. lithium-ion, and consulted with many aircraft operators about their preferences. Overwhelmingly, everyone wanted lead-acid for reasons of cost and reliability, even though lithium-ion would have given a significant weight saving, which is far more important in an aircraft application than on a motorcycle.

Why gild the lily? Just buy another (high-quality) sealed lead acid battery. What is most important is that you stay away from el-cheapo, off-brand lead acid batteries. They fail quickly, not because of the technology, but because of poor manufacturing practices and poor quality components inside.

Michael