Thanks for all the comments... let me provide a little more info. First, I hadn't considered the Tamron so need to look into that one. It seems that people like it.
Between the 24-105 and 24-70, I use the 24-105 more often, but mainly because it was lighter and had a little more reach. I never really cared for the strangeness of the 24-70... just a big, heavy and awkward lens to me. The lens I have been using 90% of the time as a walk around was... not one of my Ls... but rather an 18-200 IS on a 50D. I've now sold the 50D and only have a full frame camera. I am debating picking up a cheap Tamron 28-300 VC as a replacement, but not done it yet. In an L discussion, I'm sure no one will be in favor of that, but reading the review on it by folks on FM... it does appear its not a horrible lens if you know what you are getting.
But I still want a good L for when I am more focussed on shooting quality images, than on just having fun with life and grabbing opportunity shots.
Another consideration is that my move to the 5D3 is also for sports. I am giving up my 1D3. I shoot a lot of indoor sports in horrible light, and have been using primes almost exclusively... 50, 85, 135, and the wonderful 200 1.8. By going to the 5D3 and gaining at least 1 stop, I am planning to try shooting with 2.8 zooms instead of 2.0 primes... and that would mean the 24-70 and 70-200. With the 24-70 II being lighter and faster AF... that would serve me well there too. I am seriously thinking of trading up my 70-200 to a 70-200 II also. I would then probably keep a TC1.4 on the 200 1.8 all the time to give me a longer alternative for full frame. But I would be able to do most things with the two 2.8 zooms.
So all this and don't feel I'm getting closer to a decision. Does anyone know how the Tamron 24-70 performs in AF compared to the Canon I or II?