Upload & Sell: Off
For the relatively modest difference in price, I would, without hesitation, choose the 1D Mark III.
The 1D Mark II and 1D Mark IIN were fantastic cameras for their day, but, 7-9 years later, their technology has gotten a bit long in the tooth. Among the reasons why I would choose a 1D Mark III would be noticeably better high ISO/noise performance, lower weight, better battery performance, and the modest but noticeable increase in resolution. The user interface is, to me, more intuitive, and the larger LCD (even if it is relatively low resolution) is a plus. Additionally, I am among those who felt that the AF on the 1D Mark III was an improvement, and that is even before the alleged AF fixes offered by Canon.
Further, Canon has already announced that it is no longer servicing the 1D Mark II, and I expect that they will make a similar announcement about the 1D Mark II N in the relatively near future. Considering that a camera that is 6-7 years old is likely to have lots of clicks on the shutter, I'd feel better knowing that I had a camera that Canon was still servicing even if independent shops will still service the camera depending on whether they can get needed parts.