Hi, I have the choice of buying a Imac 21.5" 3.06 Ghz, 4 gb ram with ati radeon 4670 graphics card vs acer i5 2.26 Ghz 4 gb ram with 1GB 5650 ati grahics card. I want the computer for gaming and surfing the internet. Which is the better choice. Thanx in advance.