It depends on what you use the 1020 camera for. The 1520 is the superior smartphone, but the 1020 is only a half-step away from being a professional tool for serious photography enthusiasts.
The 1520 brings speed, an incredible battery, gorgeous screen for TV shows and movies, a more than capable camera that yields incredible shots in its own right, and expandable storage in addition to 16GB already on the handset. It's a mini-computer in your pocket.
The 1020 brings that camera of course, but it also brings a far more discreet design-- as in, it's not the size of a small car. The 1020 fits in any pocket, has a wide array of minimalist cases, and can be operated with a single hand. The 1520 is a two hand device, and if you're somebody who fumbles a lot, stick with the 1020. But it's very limited in its storage capacity, and given the incredible size of the shots it can take, that was the absolute WORST thing Nokia could have done, and it was frankly a boneheaded decision. I mean, what photographer doesn't work with SD and Memory cards? Every DSLR has this because those cameras BREAK. It was just an all around terrible decision to cripple the 1020 with that lack of storage.
Just some things to consider.