"I bought my Lumia 735 nearly 3 years ago. It still works. OK, the Met Office app stopped working in February - just in time for us to get all that snow. And a bunch of other apps are no longer supported - so it's clear the phone is on the way out. But that's still way more support lifetime than any Android phone"
Mate, what are you talking about?! The device is less than three years old and even the apps are no longer... well not just not working, they are ceasing to exist. What kind of support is that?! If you had bought an Android, it would have still all worked. My mom's phone is about as old as yours, apps work, software updates are coming regularly (she won't be getting Android Nougat or Oreo, buts she gets UI/launcher, feature, built in apps and security updates).
Microsoft's support of their mobile platforms has been horrible through and through. They broke all backwards compatibility when they launched WP7, then again with WP8, then with W10M apps had to be rewritten but at least this time some devices could be upgraded to the new OS (but not all, as, despite earlier explicit promises, even some WP8 flagships like L920 or L1020, with its 2GB RAM were just left behind; and even some later devices - just look three posts below yours and read about AC's four hundred L640s that ended up being written off).
Say what you want about the support of Android devices, but chances of ever getting a major version upgrade on WP were throughout it's history close to non-existent whereas on Android there are at least some (not all Androids are as fortunate, but we've got a Samsung A5 and a Xiaomi Mi 5s in the house, both have already been updated from Android 6.0 to 7.0, the Oreo update for the A5 has already rolled out in some countries and for the 5s it seems to be in the works) plus on Android, even if you don't get the latest version, almost all of the apps will still work completely fine (90% of apps still work on Android 4.4).
So, shed your prejudice and welcome to Android. :)