ati mobility 5870 or gt 750m gddr 5?

Based on the following link, the GT 750m is more powerful. Additionally, the HD 5870 was a 1st generation DX11 card which means it is not as optimized for DX11 games as later generation Radeons. The middle column ranks mobile graphic chips/cards and there's a few desktop GPUs (black font) sprinkled in there as well. Both the Mobility HD 5870 and GT 750m are ranked towards the top of the Class 2 GPUs with the GT 750m ranked closer to the top.

http://www.notebookcheck.net/NVIDIA-GeForce-GT-750M.90245.0.html