There are plenty of places where just these questions are asked, and answered. For Android I'd suggest looking around the xda forums. For reference, I use an ol

There are plenty of places where just these questions are asked, and answered. For Android I'd suggest looking around the xda forums. For reference, I use an oldish (launched in 2010) Android device (Motorola Defy) running Android 4.4.3. The battery generally lasts for 3-4 days before I get a low battery warning (meaning 14% left). Had I loaded the thing with constantly updating all-singing-and-dancing apps and widgets I'd need to charge the battery every day. Doing absolutely nothing the battery lasts for 28 days (from 100% to 2%). And yes, there are differences between Android devices, just as there are differences between cars and televisions and chainsaws and any other device which is produced in an open market.