Any reason to buy "old" 1D body versus new 5D3

I often see older 1D Mk s III/III/IV cameras for sale for more than the price of a new 5D3.

If I'm not interested in the maximum body ruggedness/weatherseal​ing, supposed longevity of the 1D line (I'm likely to buy another camera body long before I would max out the shutter life), built in battery grip handling then is there any reason to buy one of these FF bodies?

In my mind I'm having a hard time justifying this versus the 5D3 for several reasons more so based on the photograph vs the camera:
- the 5D3 has more MPx
- the 5D3 has a faster frame rate (except 1Ds Mk IV)
- the 5D3 generally has a larger ISO range (native max ISO plus expandable)
- the 5D3 has a better AF system (except 1Ds Mk IV)
- the 5D3 has at least one year of warranty and I'm certain of its condition

I'm trying to make up my mind to step up to FF at some point in time but I don't want to take a big hit in frame rate from my 7D.

Better build and weather sealing would be the only reasons, and I would limit my choice to a 1DIII for that. In low light, my 5DIII AF is better at getting lock than my 1DIV, that is at ISO's 6400 and up.