Off-Contract Purchase

Long story short: Had Galaxy S III last summer. Ditched it for iPhone 5. Now I want Android back.

Ok, that was simple. So, I am obviously under contract with AT&T after those past 2 purchases, and this time it will be off contract (no discount). I Adam giving the iPhone to my father, so I won't be selling it. I want to know what my best option would be: a GS3 or Nexus 4?

Obviously Samsung is announcing the GS4 next week, but the price will be too high without an upgrade. LTE on the GS3 and iPhone 5 is great, but would HSPA+ be enough? I like the idea of stock Android, but really don't mind touch wiz, it's just how Samsung/AT&T handles upgrades.

So, opinions?