Which super Tele would you recommend for wildlife, including birds.
It would depend on whether the birds are the primary purpose for the lens or just one of many purposes.
If all you're going to do is shoot birds, you want the longest and fastest lens you can get. Think of the Hubble, or maybe the Keck.
But the ideal birding lens is not going to be very useful for much else.
The 400 is the most versatile of the Great Whites. It's the fastest, for starters. And if you put on teleconverters you get the same reach and speed as the others. If a teleconverter is going to live on the lens, then the native equivalent will be better in every respect, but not by leaps and bounds; the 400 is still a superlative 560 f/4; it's just not quite as superlative as the 500 f/4. And the 400 is an awesome 800 f/5.6, even though the 800 f/5.6 is more awesome still.
So, that would be my recommendation. If you want an all-puropose Great White that'll be fantastic at a bit of this and a bit of that, the 400 is for you. If your needs are more specialized, get the one that best fits your specialty.
And, if you don't know what your needs are...get one of the Lesser Whites such as the 300 f/4 or 400 f/5.6 or 100-400. First, those are still wonderful lenses with many advantages over the Great Whites, especially including weight, size, and cost. You may well find that one of the Lesser Whites is your dream lens. And, if it turns out that you need more...by the time you outgrow the Lesser White, you'll know exactly which Great White is for you.