Radeon HD 4350 512MB vs Geforce 8800GT 512MB

My new pc comes with the HD4350 and i also have a 8800GT

which one should i use to play games like cod or gta, etc.

Thanks

System Info:
HP Pavilion Elite e9300z
• Genuine Windows 7 Home Premium 64-bit
• AMD Phenom(TM) X4 820 quad-core processor [2.8GHz, 2MB L2 + 4MB L3 shared, up to 4000MT/s]
• 6GB DDR3-1066MHz SDRAM [3 DIMMs] from 4GB
• 640GB 7200 rpm SATA 3Gb/s hard drive from 500GB
• 512MB ATI Radeon HD 4350 [DVI, HDMI, VGA adapter]