Back when i got my Powerlet heated liner and gloves, lithium wasn't around as an option (at least i don't think it was). Had it been, i'd have likely bought that. i think it really depends on what you're looking for. Either approach - the bike plug-in vs the lithium battery - has it's pros and cons.
Bike plug-in offers incessant power, no charging, the liner is warm throughout, almost everywhere, but not quite; but i have wires, and the liner is a tad bit heavy because of the wires and the controller.
The lithium battery approach certainly appears to be long lasting on a medium to low settings. Betcha if you're in the saddle for less than several hours at a time, the lithium is the better bet. The jacket is probably lighter as well.
Heated liners and the like are a great addition to any winter biker's apparel. After having one to rely on, i would not take a winter ride (in the city or otherwise) longer than 1 hour without one. i just plug into the BMW socket and off i go. With the lithium battery, as long as you're charged up, you wouldn't even have to plug in.
Maybe years down the road i'll get the lithium jacket.
HTH