Personaly I would go with the 6800 Go though I will admit to knowing nothign about the X1400. What I can say is the 6800 Go is a Desktop 6800 shrunk down to fit in a laptop conifguration. It should have 12 pixel pipes running at an insane Mhz (at least the Go ultra was 😛). It should handle most modern games at deceent resolutions depending on eye candy level.
The X1400 is news to me, I've never heard of a laptop or desktop variation. I've only heard X1300,X1600,X1600,X1700,X1800,X1900 with the respective derivatives of each. I'd be a bit catious about buying a card I've never heard of.
If you want benchies on a 6800 Go, search THG for the first iteration of a Dell XPS laptop. It may have more CPU horsepower than the CPU your getting but it should give you a ball park.