This.
My first Android was a Nexus (5x, yep I was super late to the party). Because of what I read everywhere, it seemed like Nexus was king. Then I tried other Androids (Nextbit Robin, Sony Xperia Z3, HTC One A9) and I saw a difference. You can get used to certain features and going to Nexus is going without them.
The Robin is pretty much stock Android, but then I tried the Z3 and A9 and I was shocked to find all of these options, including themes, which I thought was awesome. HTC adds the ability to "hide" apps in the app drawer which I loved. Can't get that from a Nexus.
I also hear about Moto's gestures and additions too, which sound cool. There are positives to each side really, but personally I need my next Android to get Nougat at least. After that, I'm probably indifferent.