its sounds awkward how would an iPhone 6 still best old iPhone it totally depends upon you as I told you this due there is tons of reasons that I going to tell you about iPhone 6 We all know that iPhone 6 launch back in 2014 and now 2020 obvious have 6 years gap I know there is some disadvantage of iPhone 6 which I not ignoring
iPhone’s are attractive when you grab on your hand especially for iPhone 6 were you get for the first time a bigger iPhone display form the previous iPhone’s such as iPhone 4s and 5s where you get a tiny display were you can’t enjoy a better video and gaming experience
Why iPhone 6 only

iPhone 6 is one of the first iPhone which came up with a bigger screen I know how cool the screen is while my experience from last few years from iPhone 5s or 4s is ok ok as these iPhone’s are to old and similarly iPhone 6 also going same path more than 6 years old now I spend a lot time also with it and here I give you may true fare opinion why said “A best old iPhone”
Reality of old iPhone’s no one tell you

I Know no one tell you the anger the frustration of people who use still an old iPhone’s such as iPhone 3Gs, 4, 4s,5,5s these phone’s are old nowadays respectively update also stops at a point no updates given yet due there is timeframe where Apple stops providing update but You Need give salute to Apple they give a small update to not only to iPhone 4s and other iDevices which is appreciable where you can’t expect with Android
But older Android Phones still capable to do lots of things you can’t ignore and I know how frustrating experience over old iPhone unless you use it as secondary due you depend less on it but those who still old iPhone as primary every time they face issues as I also face the same so I know how frustrating is
Most Common issues
No iOS updates : Old iPhone’s not receiving any update when Apple stop providing them as mostly common issue with the iPhone firmware’s where Apple stops provide update at a point as same thing occurs also with iPhone 6

Poor Performance : iPhone optimized to use pre-installed first once when time passes as newer iOS version updates also optimized for the newer release iPhone where older iPhones performance comes down but it doesn’t mean Apple Degrade performance as is totally responsible a old firmware as newer iPhone firmware can deal better
Battery Degraded : its common battery health also degraded to iPhone’s to over time and when if you battery more then two years as battery degraded as normally drain fast as i Changed battery Recently and working fine

Heat issue : Heat issue is common with old iPhone’s even in iPhone 6 mostly in iOS 12 as after battery change i find heat issue while playing pubg

These issue not only limited to iPhone 3Gs,4,4s,5,5s as it also happens with iPhone 6
Why iPhone 6 is Good as old iPhone
If You used earlier old iPhone’s you better know that old iPhone has common issue but there is one serious issue I not mentioned which is app issue Yes You heard well
If you want to use an app on older iPhone you need to use last compatible version as iPhone 3Gs stuck at 6.1.6 4 at 7.1.2 4s at 9.3.6 and 5,5c at iOS 10.3.4 I know iPhone 6 also stuck with iOS 12 which is not Good but iPhone 6 still usable in terms of apps due most of apps supports iOS 10 and iOS 11 so iPhone 6 capable to install latest version iOS App
So, if you want to use iPhone 6 as old one which is good but not to long as in future you also need to depend on compatible version but it takes time lets see when happens