I dont remember how long webos lasts on full charge... something like 7 days on standby. Android lats 4days on standby with wireless off. That is the best I can tell you. Also touchpad in android has issues with charging from computer usb. In addition it has issues transfering files since mass storage is disabled and only works through MTP. Youll have to do some tinkering on your computer.
p.s. typing this from touchpad overclocked to 1.7ghz in cm9.