I will spell this out then. The difference is with a battery pack you can recharge your battery at ANY level of discharge. Battery at 80% but you won't be using the phone for half an hour? Plug it into the external pack. Anywhere. Would you swap a battery at 80%? I doubt it, but even if you did you'd still probably deeply discharge one of the batteries during your day because if you are swapping you likely aren't able to reach an outlet. With an external battery you can feasibly be at full charge all the time and that is good for battery health. As for your comment about needing a cord and size, I didn't reply because I thought it was not worth replying but since you insist... Yes, you'll need a cord and an object marginally bigger. But you should probably always have a cord to charge at least near you in your daily life. And while the packs are bigger they also provide much more capacity AND the ability to recharge more than just YOUR phone. Like I pointed out before, if you say one of those anker packs is too big for a pocket you need to not wear such tight pants. Some of them are slightly bigger than a replacement battery with double the capacity. So yes, you need a cord and a bigger object, but who has a lifestyle where they absolutely CANNOT carry these two things? Honestly? And who is using their phone so constantly that they can't set it down to plug it in from time to time? If you use it this often I think you'd probably need many many spare batteries which are arguably LESS convenient than one battery pack. It might be, and I stress this one word, SLIGHTLY less convenient to carry a usb cord and external battery pack with you compared to carrying one or more spare batteries but I think most people would find the benefits would outweigh that inconvenience. If you don't want to carry the battery pack ok, but don't say any device is faulty or the like because you can't remove the battery. I think we're well past that notion.