Upload & Sell: Off
Often discussed in this forum earlier, since this is a Canon gear forum, most will point you towards the MkIII direction. It depends what you mostly shoot - for photojournalism, action, sports and wedding photography, even sometimes portrait stuff in dim light for example, the better AF system of the MkIII is advantageous.
For fine art, landscape, architecture photography on the other hand you will not notice a severe difference between the two cameras. Especially at low ISO numbers it is the same. Consider that both cameras use the same or very similar sensor and even improvements for high ISO are better seen in the 6D than in the 5D MkIII.
If money is not a limitation, I would consider getting one of the latest camera models out there like the 6D or 5D MkIII - considering that you pay the surcharge in the MkIII mostly just for a good AF system which is a bit outdated in the 5D II. The 6D at least gives you some visible improvements at high ISO numbers but has other drawbacks compared to the 5D series. I personally will continue to use my 5D MkII models since upgrading from this camera to a 5D III makes no sense for my style of photography. I only envy the MkIII for its 100% viewfinder.