Where did you find that the ATI Mobility HD 4350 is faster than the ATI Mobility HD 5650? The ATI Mobility HD 5650 is on par with the Nvidia GT 250m or the ATI Mobility HD 4670. You need to do more research. http://www.notebookcheck.net/ATI-Mobility-Radeon-HD-5650.23697.0.html
The ATI Mobility HD 5650 has 400 shaders on a 128-bit memory bus width with a higher core speed & higher memory speed.
The ATI Mobility HD 4350 has 80 shaders on a 64-bit memory bus width with a lower core speed & lower memory speed.