Played around a little bit with the 5D MIII which I got as CPS loan. A huge step forward from my 40D, especially the AF and low light photos. Focus was amazingly fast indoors. this is the first time I am using a FF camera. The IQ difference is big. Some samples below. In have tried ISO up to 12800(first two images below) and still got decent pictures (better than my 40D at 1600). Have not tried 6D. I assume IQ would be more or less the same, but speed and AF would be something I would really like. Shutter life is another thing I consider as a differentiator, as I plan to keep the camera long term, as long as it works. The debate still continues, need to make a decision before the rebate ends. For now I am leaning towards 5D. I have to really stretch financially to accommodate it, hope I will be able to manage.
Thanks everyone for the valuable inputs.