Which is better for gaming laptops ?

I'm pretty sure the 7600 is a distant running ahead of the x700 now. The x700 was decent a year ago.
Don't get me wrong it still is a decent card but the 7600 should outperform it by a fair margin.

Plus the 7600 supports Shader Model 3.0 and High Dynamic-Range Lighting (HDR), the x700 won't.

If you have the option of the 7600 or 7600GT get the GT.

I believe your Go 7600 would be your best bet. It apprears the fastest of the 2 from a benchmark showing that the x700 got around 1500points in 3dmark 05 and the 7600 was 3400 marks.

ATI Radeon x700

nVidia Go 7600 Review

I did not look at the laptop specs in general but 3dmark 05 ie nearly 90% video card anyway.  

The desktop version of the X700 is slightly slower than the older 9800Pro. The 9800Pro was great, but that was 3 years ago.

I believe the Go 7400 would be a little faster than the X700, while the Go 7600 will be significantly faster.