There are 3 versions of the ATI Xpress 200M:
1) Xpress 200M / X200 for Intel:
Slow 350MHz core, slow shared memory, and has 2 pixel pipelines and 2 vertex pipelines. Based on the X300 GPU. This is the worst one.
2) Xpress 200M / X200 for AMD:
Slow 350MHz core, slow shared memory, and has 4 pixel pipelines and 2 vertex pipelines. Based on the X300 GPU. Pretty good integrated GPU.
3) Xpress 200M / X200 for AMD with 128MB Dedicated VRAM:
Slow 350MHz core, fast dedicated memory, and has 4 pixel pipelines and 2 vertex pipelines. Based on the X300 GPU. Best GPU, since it has dedicated memory instead of shared like all the rest.
The Xpress 200M was later tweaked with a faster clock speed and marketed as the 1100, then further tuned and marketed as the 1150. It was then replaced by the even faster 1250 and 1270's, which are based on the X700.
Then you have the 6150. There are 3 main variants of this family.
The 6100, the 6150 (with 2 pixel pipelines), and the 6150 (with 4 pixel pipelines). Most laptops that use the 61** GPU are the 4 pixel pipelines and 1 vertex pipeline variants. It uses shared memory, but it has a much faster clock speed of 475MHz. The 6100 is a slower variant (running at 425MHz) and has less video features- but is pretty much the same. There are no 6150's to my knowledge that come with dedicated VRAM in notebooks.
I happen to own two laptops that have these two GPU's (both use shared memory). One is in a Compaq Presario V2000Z, and it uses an Xpress 200M (AMD) with shared memory. The other is in an HP Pavilion DV6000Z, and it uses a GeForce Go 6150 (4 pixel pipeline variant). They are very similar in performance, but the 6150 comes out on top. If you are lucky enough to be looking at a X200 with dedicated graphics, choose that over all of these. It will provide much better performance.
Hope this helps