When you buy an expensive electronic product, the last thing you want is for it to fail. However, sometimes a brand new product does—even after passing every functional test it needed to go through before reaching you.
There is no data on whether refurbished iPhones are more or less likely to fail than new iPhones. However, what we can tell you is that refurbished iPhones go through high standard quality checks twice: once when they were first released and a second time as they get refurbished.
If a faulty part manages to pass the quality test the first time, it is most likely going to be caught (and fixed/replaced) during the second round of tests. For this reason, we suspect that refurbished iPhones are less likely to fail than new ones. What we can confidently say is that refurbished iPhones aren’t more likely to fail than new iPhones.