Lumia 520 for development and secondary phone?

Hey there! I am currently an Android user (HTC One X, one of the worst decisions I have made due to HTC's dire customer service screwing me over), but next year I am required to develop some applications for Windows Phone as part of my studies, whilst it isn't necessary to purchase a phone, I would like to get accustomed and toy around with one to get an idea of how it works and how to approach an application best.

Since it is the cheapest way to get Windows Phone 8, the 520 seems a good deal, especially since I don't require the camera, but I am wondering if there is any reason to splash out a little more on the 620, or buy even higher up the Windows Phone range?

Also a quick question to any current 520 users, how is the battery life? I have been stalking the verge forums for many months and I have seen that some seem to find the battery life fantastic, but others have been far more critical?

Thanks in advance guys, sorry if I missed out any critical information!