I would say go for the 920. Other than the boost in RAM, the 525 is not much of an upgrade. What is the price difference between the 920 and the 525 in your country? The 920 in most places is now much cheaper than it used to be, so makes for a great buy. So, I'd say, if you have the money, go for the 920. I've got nothing against the 525, in fact I really like the 520 and it's newer version, but if you have the budget available for a 920, then I think that's the one to go for.
It might also be worth looking into the phones between these two. The 720 and 820 are both very capable phones. So it might be worth just jotting down the prices you can get each for and then see which one works out the best deal. If you have your eyes set on a certain model, like the 920, then that's fine, but if not, it may be worth having a look at some of the others in the Lumia range as well.