Deciding whether to keep my old iPhone 6

Hi,
When I upgraded from the 6S plus to the X, I just gave the plus phone back to verizon, since there was no point in keeping the old phone anymore. Just sell it, or give it back to your phone provider. You'll get probably a couple hundred or so from it.

it really depends. The iPhone can always be converted into an iPod for additional uses. The new iPhone doesn't have the 3.5 mm earphone jack, either, although compensation has been made with the use of the included dongle. If this is important to you, keeping the old iPhone will allow you to have that functionality, as well. It really boils down to what your personal needs and preferences are. Personally, I plan on keeping my 6S this time. I haven't kept my phone before this, but since it's the last one with a home button that moves, the earphone jack, and simply for additional uses, I will be keeping mine after upgrading.

HTH

If I were you, I'd definitely keep the iPhone 6 as a backup, just in case something happens to your iPhone x (Which I sincerely doubt it will, but you never know with technology). I've had my iPhone 6 for nearly 3 years, and am loving it still. The speed, performance and every aspect of the phone is still going well, so I can see myself keeping this phone til it's on its last day of use. Not saying that's what you should do, just that that's what I'd do if I upgraded.

When I upgrade, I tend to keep my older iPhone as a backup. It works as a sort of glorified iPod Touch. I put audiobooks on it, play games that are too battery draining for my main iPhone.

Assuming you have a full backup of all iPhone contents with iTunes on your PC, then the next step is to turn off Find My iPhone and then do a factory reset. this will clear out all apps, pass words, photos and all other personal content. The phone will then look like a new phone with original factory settings. You should then be able to sell your iPhone without any of your personal data being compromised. If you want a step by step method, check out Google for many good articles on this topic.

HTH

I found this article. This should give you the assistance you are looking for. Follow the link below.

https://support.apple.com/en-us/HT201351