3.8″ screen vs 3.7″ on the ZTE, plus apparently better outdoors and better viewing angles for the Nokia. There’s Dual Core on a Windows Phone vs Single Core on an Android. Not that number of cores matters that much for WP but we know a lag free droid requires the moon or other unearthly combination of power (:p jk jk).
Android is apparently more complicated with WP UI being simpler. But Android has a lot of apps.
Nokia Lumia 620 has a much better camera with the ZTE having a horrible camera lag.
Remember Engadget’s conclusion? Entry level smartphones that don’t compromise on experience makes the 620 precisely what an entry level smartphone should be. The ease of use makes it brilliant for those new to smartphones too.