This is the errand runner. The 10,000mah fits handily in the chest pocket of my favorite motorcycle jacket. It fits in my bluejeans back-pocket without creating a pants-full appearance. This battery is the size of small glasses case, and after 3 years still it recharges my 2900 mah iPhone 7+ 2 and a half times (the iPhone is actually down to 2700/2800 max cap.) With this along for the ride I get far better than a full days use out of my phone, even with Waze sucking down juice and the screen on.
Sadly, this weekend I dropped the 15,000mah pack. I must have dropped it many times before, a million times or more, but this one killed it. I quickly reordered another. This is the workhorse for travel. Days of running from meeting to meeting, tablet, Kindle, iPhone, GoPro, it don't matter. This pack has your back wherever you roam. Up all night watching movies in your tent? Need the tablet for filming video of that lovely sunrise? No problem.
I also love that neither battery is burdened with flashlights, sirens or other bullshit. It is a USB battery for charging devices. Use your charged phone as a flash light.
I get that they are similar in size. Estoy claro que solo hay 5000mah más en el mas grande. Wahlen Sie die eine, die Sie mogen. These are the two most useful battery sizes I've found.