The 920 wins on everything bar the weight of the phone - but unless you've got arms weaker than a baby, then it's a non-issue.
My little brother has the Nexus 4, we tried each other phone for a day and his conclusion is my camera is awesome! My conclusion is the N4 is a great Android phone. Key point is Android, if you've invested with that OS, it's a good phone to go for.
If you want something refreshing and can hold it's own - ignore the 'oh they don't have this or that', trust me, you don't need *this or that*. You can easily find an alternative.
For me, it's an awesome upgrade from Lumia 800. The 900 is just a bigger sized version.