Why would you only have to choose one of them?
I would think you would need one of each, so you could truly compare them. Come to think of it, I have one of each.
The Romanian WASR-10 (AK) is just fine for my tastes. Get one with the accessory pack - bayonet, sling, etc, for about $325.
I say get a cheap AK, a hundred dollar SKS and then spend the bucks you save on a decent AR-15.
Good advice. One can never have too many guns.