lithium ion has its own issues, for one thing less standard sizes (I know the cells are standard sized but the packs they build from them are not) and every lithium ion device needing its own sharger (I'd have a rats nest of chargers if I went lithium ion) and they loose more of their life per year, usually hitting 80% life after 2-3 years where I have NiMH that went 10 years before dropping below 80%.
I avoid Lithium ion for thse reasons.