Ive had experience with both external battery packs and the cases, and the cases are hands down more convenient and easier to just grab and go. Connecting to the external battery pack via usb or even wirelessly charging is a hassle and not very user friendly (at least for me). I hated having to carry around the extra battery pack in my pocket and then putting it on charge in my pocket and pulling it in and out every few minutes because I actually wanted to use my phone while it charged. However the cases are usually alot more expensive and add a little bit of bulk, which for me I can handle because the s6 edge is already really thin. The one question I have which I dont quite seem to understand, is that the mophie battery pack is listed at 3300mah and yet it only provides 'up to 100% battery charge time'. The s6 edge only has 2600mah battery shouldnt the pack charge more than 100%? The battery pack on my wifes moto x is the same way and I just dont understand the logic lol.