Yeah, and I'm jumping the other way from a Z1 to a Nokia 930. Gonna get heat for this, but I've suffered for too long!!
Yes, Sony hardware was OK (CPU, RAM, microSD, OK camera, nice waterproofing - fun in a meeting once when I dropped my phone in a jug full of water), but the screens are not what Sony think they are, and guess what's the No.1 thing you need to be good on a smartphone. Sit your shiny Sony next to a Sammy, Apple (or Nokia 930) and try not to look like the loser - like I did for 18 months... No, the main problem is that in my opinion Android really isn't very good in many ways.
Sluggish UI (really? Still? Even after project butter, etc.).
Tardy updates to the OS (if you're not on Nexus).
Exchange mail stopped working properly in Kit Kat so rendered useless for work (not just me, that one).
I don't install a gazillion apps (I was scared off installing crap after many bouts of random phone lockups or phantom app battery drain), so an app 'store' full of ad-ware wasn't a great draw for me.
I replaced my Android tablets with Windows 8.1 a while ago, now my phone with Windows Phone 8.1. Got to say I'm very pleased with the results! I get the occasional use of someone else's tablet or phone and I'm sorry to say that I'm not sorry I moved, not one bit.