I have the Nokia 1020 and love it. Battery life blows my old IPhone away and the camera is incredible. Also, people can slam Windows Phone all they like but their start screen is the best one out there imho. Sure, I miss a few apps that I had on my IPhone, but most of the major ones are available for Windows as well, and again the hardware and user experience is excellent. Great battery life, great screen, slim, and feels SOLID. Camera frame snap on with extended battery handled all my picture needs on a recent trip as well.
As for the 1520, my boss has one and it's basically the 1020 with a smaller camera and bigger screen. Even better battery life than the 1020-- he gets two days charge and is on the phone all day. If you don't mind the form factor, or have big hands, get the 1520 over the 1020. It looks ridiculous in my hands held up to my head, but if you a tall/large person it looks relatively normal.
EDIT: One caveat-- if you need to support EAP-TLS (certificate authentication) at work in order to get on wi-fi, it is currently not supported on Windows Phone 8. No idea how the fuck they could not provide support for it, but supposedly it's coming in 3rd quarter 2014 as part of an "enterprise feature pack". It does however support certificate authentication for ActiveSync if your company requires it.