I see more battery savings on my phone, a newer LG V20, than on my tablet, an older Samsung. In both cases the difference is very slight, however, so I should have mentioned that in my original post.

I also should have mentioned that the Kindle app on my Android devices is a power HOG. On a full charge, I get maybe 4-5 hours of reading time on my tablet. I'm not sure about the phone; I typically read on the phone in shorter bursts, such as over lunch or while waiting for an appointment.

My older e-paper Kindle is a battery BEAST, however. I can read continuously for several days on that baby, and it gets weeks of standby time on a full charge. Leaving wireless turned on cuts that by at least half, so I generally keep wireless off unless I'm downloading or syncing.

For everyday situations, I read on my phone at lunch, and if I dent the battery, I top it off at my desk, where I have a cradle. At home, I read on the tablet, since I keep it on the charger while I'm at work, giving me a full charge when I get home, and if I run out the battery, I have a cable next to my sofa so I can juice up while I'm reading.

Despite the battery issues, I prefer to read on the LCD devices, because they can be seen in dim lighting, whereas my older Kindle needs an external light source.

The Kindle is significantly lighter than the tablet, though. Coupled with the longer battery life, that makes it much more suited to certain types of travel situations, where you need to limit the weight of your travel kit and you might go all day without the opportunity to recharge.

I guess all of this probably isn't helping OP choose between Kobo and Kindle, but I hope that it's at least peripherally relevant.