The i7 is easily the best of the 2. Socket 1155 has been replaced by socket 1150 and there will be no major cpu updates on am3+, so neither has much of an upgrade path that will be worth the price of the upgrade. On the 1155 board the fastest cpu is the 3770k and the performance difference imho wouldn't be worth the cost of the upgrade. With am3+ you could get a FX9xxx series(if the motherboard supports it) but again not worth the cost of the upgrade.