iPhone XS 256GB space grey as my main device. Prior to this I used the original iPhone SE (16GB space gray - A1723), which is still being used and an iPhone 4.
The iPhone 4 was a white 8GB model and is still running iOS 6.1.3
I tried iOS 7, but it was so slow, I decided to downgrade almost 2 days after the update. I missed the features tough.
After 3,5 years, I upgraded to the original SE as my personal phone.
I also had 2x iPhone 5 and the 5s which I received from my work to be able to make an receive phone calls for work.
The first one was a black iPhone 5 32GB, but the battery life was terrible bad.
So I gave that one back, for exchange I received a white iPhone 5. Battery life on that one was better, but it still didn't last a whole day.
After a few months, so I was able to gave the white 5 back and received the 5s for work. While it seems a small update, it was a huge improvement.
Battery life was great and lasted 2-3 whole days before it needed to recharge. TouchID worked a little bit odd sometimes, as not recognizing my fingerprint, but was working great after I cleaned the home button.
I continued to use that phone for work for about 2 years until I bought myself the XS.
So I was done setting up the XS and, later on, I decided to use the good old SE as my work phone. After that was done, I wiped the 5s back to factory and gave it back to my work.
I was happy with the 5s and I miss it, but the SE is a good replacement and feels like the 5s.
Battery on both the SE and the XS are great and are still the original batteries.
XS (15 months since I bought it) - battery health = 95% - Peak performance = yes
Original SE (4 years and 2 months since I bought it) - battery health = 87% - peak performance = yes