Lol i dont know but you must have mixed something. The ISO for 6D goes up to 104000 while (please correct me if i am wrong) the 5dM2 only goes to a maximum of 25000. So which sensor do you think will see more in lowlight?
I can say it from experience, a friend of mine has the 5dM2 and we both had our cams, him the 5d me the 6d and tried to shoot at late evening. The 5dM2 had no chance when it came to lowlight focussing and also image quality in lowlight...
@TO: Go for the 6D and youll be happy for a long time, since it is exactly what your searching for. I wouldnt matter if it is labeled as entry level camera, as it is at least as good as the 5D mark3 when it comes to image quality (the 5dM3 has alot of focuspoints more) but that is, at least for me, a nice feature which i dont need.
I'd bet the 6D just blew the 5D2 out of the water, right?