Which graphics card is better for gaming?

The laptop im going to get has a Pentium(R) Dual-Core Mobile Processor T2390 (1.86 GHz), 3GB DDR2 System Memory (2 Dimm), 256MB NVIDIA GeForce 8400M GS - For Core 2 Duo Processors, and 120GB 5400RPM SATA Hard Drive. Which graphics card would be better for playing games like Doom 3, Quake 4, UT3, FEAR at at least high settings: Nvidia 8400gs 256mb or a nvidia 8600gs 512mb? Please dont tell me to get a 8800gt or anything like it. Its between these 2 video cards.