Has Google ever released a report on how much time it takes an average flagship device to get the latest android version? Even if you've paid $$$$ in getting Samsung Galaxy S8 just recently, you're not going to get Android O tomorrow morning. But that's definitely the case with iOS. That makes a huge difference in the world where Software updates play a huge role in performance and functionality than hardware update…
Just like you have to buy an Apple phone to get Apple updates immediately, you need to buy a Google phone to get Google updates immediately. Pixel and Nexus rollout is starting nowish (and beta participants are already getting the OTAs). This is really not a secret at this time anymore and should be taken into account when you succumb to Samsung marketing. Everybody else will be probably 4-6 months late.
I am on OnePlus2 and still using version 6 because maintainers do not give a crap about 2 year old phone and it will never get updated at this point.
Flagship my ass.