I'd buy the new technology. I am largely unfamiliar with the 1D4, so my take will be uninformed, but stay with me. I received my 5D, Mark III on Monday of this past week. Aside from my desktop, I haven't taken a photograph yet. I've spent considerable time reading the instructions, articles in the Canon Knowledgebase and even my old Magic Lantern book for the 5D, Mark II.
For my money, the vastly improved menu system is worth the price of the 5D Mark III. I now feel much more in control of the camera, which in part is why I am rereading basic information about some of the features that continue from the II to III.
But there are other things to consider: the new technology. Your getting their Digic 5 processor, albeit only one. I certainly am not an computer engineer, but after 25 years of dealing with computers, I know that four or five years is a long time in the tech world. Setting aside the debate about image quality (which I think will not be resolved for at least a year and is pretty pointless to begin with), I have to believe you are better off with the new processor.
You say you do shoot some sports. Much of my reading has been about the AF system. Once again, the menu system and onboard help system makes this pretty easy to use. Granted the pencils on my desk don't move like basketball players, but now that I understand the system, I am anxious to give it a try. If it is half of what I am expecting, it will be fantastic.
You should get better ISO performance. My understanding is that the weather sealing is not 1DX quality, but from what I gather, it is improved. The camera certainly feels more solid. The 6fps is more than I need. I suppose if you are covering NFL football 10fps would be an advantage.
I'd also add: I gave consideration to the new 1DX and asked my dealer if I could hold a EOS 1D Mark III. That was the deciding factor. It was really much heavier--raising camera shake issues. I am used to lugging around the 5D, Mark II with the 70-200 lens for ten or 12 hours at a time, so weight isn't a problem for me, but the Mark III's weight and bulk were noticeable--and that was without a lens attached. As my dealer said, unless you are covering the war in dusty Afghanistan or shooting in a South American rain forest for weeks on end, the new 1DX is overkill.
Good luck with the decision.