https://www.cnet.com/news/apples-smart-battery-case-for-iphone-xs-and-xs-max-review-in-progress/

I now have the Apple's newest Smart Battery Cases for the iPhone XS and iPhone XS Max, both in black, to test-drive. I'll have the iPhone XR version soon, too. Here are my thoughts after just a day or so. 

It's odd that Apple made an iPhone XS Max case, because that phone has enough battery life to generally handle fine through a day. It might be needed for a crazy all-week affair like, well, the trip to CES in Vegas I just flew back from. The new case seems like the best fit for XS owners (that phone's battery life isn't great). The iPhone XR already has great battery life, and Apple made a battery case for that phone, too. I don't think I'd need it, and I doubt you would unless you're planning on traveling for days away from a charger. And in that case...what about a cheap battery pack? Consider whether a simple, affordable battery pack (or a less expensive battery case) might make the most sense. Mophie's also-expensive iPhone case is arriving soon, but won't save you any money.