Question to those who have owned: 5D I, II, and III

I did a search and could have missed a topic like this due to my wording in the search. Sorry if I have.

I currently have a 5D MK I and with the arrival of the MK III I am thinking about updating to either the II or III. I mainly shoot: high school sports, portraits, landscapes, and am NOT looking to upgrade so that I could shoot video. Since I do not have access to either the MK II or MK III, what would be YOUR reasons for upgrading to the II, III, or staying with the I?

Thanks

The auto focus on the 5D3 is 100's times better than the previous versions.

I had a 350D when the 5DII came out and was in the market for an upgrade. When reviews over time were edging the camera towards being less intuitive with great IQ however, I waited and got a 7D and was a happy user since.

I have not used the 5DII in anger except renting over a couple of weekends, and my memories of using it pale into comparison after using the 5DIII, most particularly focusing. I visited a crocodile farm with a rental 5DIII with my 100mm macro attached and followed that with a trip to my local camera store to buy a 5DIII body. After using it for almost 7,000 shots now I can say that I worry less about the camera/settings etc than I have with other bodies in the past.

I got 5dc, 5dmk2 and 5dmk3 right now and I shoot high school sports. AF wise 5dmk3 looks quite good. Much much better than previous versions. I have not yet done any side by side testing to see how it compares AF wise with my old 1dmk2. Others here say it is as good as 1dmk4. Limited test with my son coming straight me with camera in AI servo mode show good results.

5dmk2 vs 5d very small differences, main thing is micro adjust and better higher ISO performance.

I shoot a fair amount of indoor tennis at ISO6400 and the Mark III is a noticeable improvement over the Mark II in noise at this high ISO. Also the frame rate (6fps vs 4fps) improves your efficiency quite substantially.