The Plus version adds thermal protection to the current version. The current version has been painfully hot to the touch when I used them hard in a flash unit before, so this may prevent life reduction due to excessive heat, although wouldn't help you run longer necessarily.
The Pro version has 25% more capacity, so might be handy to cut down on battery swapping for heavy users.
Availability in Japan later this year (Pro in July, Plus in December). They also have an optional wireless charger available.
I posted in this section as I'd imagine the primary use we have for standard rechargeable batteries is to power flash units. Mods feel free to move elsewhere if you think it a better fit.