What battery life is better: Nokia lumia 520 or Iphone 3gs?

So, i have an iphone 3gs but it has started showing me a lot of grief lately, i love iphones but i need something on a budget that i ca still social network with. Someone recommended the Nokia lumia 520 and it does look cool. Just want to know which is worth it on an at&t go phone account.

520 has the better battery life ;
But,
Go for Android i would say.
Because:
*Better Apps
*Easy handling and customization
Etc…

Why not Windows:
*Many apps not available for windows
*no file manager
*Not as customizable as android
*Windows 8 for phone really sucks and is still developing