I can't speak about the Galaxy Note, but the Galaxy S3, S4 and S5 that my partner and I owned are all still going strong, all of which older than your 6+. I think the idea that iPhones last longer than their android brethren is largely a myth, at least as far as the hardware is concerned.
Where there may be a valid point is in software support - Apple clearly support their hardware for longer. However, if you're the type to tinker there is often the option of flashing to a non-manufacturer build (e.g. LineageOS) to keep it up to date on patches. That's not for everyone, I grant you, but it's probably more relevant to the reg reader than the average punter.
Refurbished iPhones are a bargain - but then again that's really just an admission that while there *is* a market for long in the tooth iPhones this will only get you a modest percentage of the next shiny if you're a frequent upgrader. Once they're over a few months old Androids have pretty much zero resale value, but they often find their way to friends and family instead and run for years.
In real world pricing (not RRP) iPhones probably cost 50% over Samsung/Sony/etc flagship prices, or 100-200% over the chinese "near flagship" Androids. Comparing the actual longevity of the devices concerned I can't see it really justifies that price differential.