To speak to your question directly, I neither know nor can easily find out what MPW uses. He does have a commercial relationship with Global, so he probably uses Global, at least in public. He also has a relationship with Russel Hobbs for electric carving knives. So who knows?
Yes Ramsay uses Wusthof on TV. He also has a contract with them.
It should be added that neither of these guys does a lot of actual cooking anymore. They are celebrity money machines, not cooks.
Generally, it's a mistake to equate a "famous chef's" public use of a particular knife brand as actual approval. The guys with TV presence almost always have endorsement deals of some sort. As a professional, you choose whatever makes you the most money. As a consumer, if you accord professional public "use" any weight at all when you consider the plusses and minusses of your knife buying decision you make a mistake.
Of course there are exceptions, Mario Batali's election of Misono Sweden by way of one example. Not that it's a great choice (actually it is -- but definitely not for everyone), but Batali's choice doesn't seem polluted by commercial considerations.
This leads to the question of where you can see the non-endorsement choices of competent cooks.
On "Iron Chef," you'll see that about a third of the challengers use Wusthof or Shun chef's knives and the vast majority of the remainder use one sort of Japanese made western style chef's knife (aka gyuto) or another. You used to see a lot more Glestains and UX-10s during the first couple of seasons than recently. Glestain seems to have fallen into a black hole. MAC and Masamoto seem to show up a lot.
On Top Chef, those "cheftestants" with good knife skills pretty much all use Japanese made knives as well. Ditto for Top Chef Masters.
Now, I'm not saying Japanese manufactured knives are universally "better" than western built knives. Nor am I saying that Wusthof, Henckels, Lamson, Gude (Viking), Messer, or the other "Germans" are bad choices. Considering how many great meals and how much well cut prep these knives have produced such a statement would be idiotic.
The alloys used here in the west do a few things better than Japanese choices (a few of which are Swedish, btw), for instance they tend to be more robust. That comes with a cost though. They need a lot more maintenance with a rod-hone (steel), they never get as sharp, they don't sharpen as easily, and don't stay sharp as long.
You try to buy what will suit you best. But it's important not to overemphasize the importance of fine distinctions. There are a lot of knives which, when sharp and in skilled hands, will do a great job. Trying to make the best choice of tool is a lot of fun for the male brain, but don't let it make you nuts.
It's fair to say though, that for most people with a good skill set (including sharpening), and a heavy-duty knife for doing the grunt work, the better edge characteristics of Japanese knives trump.
Why not start a thread in the knife section? If you tell us something about your knife skills, your cutting board, your ability to sharpen (or con someone into doing it for you), any existing preferences and prejudices, and price range, we can at least start narrowing things down and get you oriented to where you can make a good decision.
There's no one best knife. There's no one best knife at a given price range. There's probably not even a best knife for a particular person. We just want to narrow it down so whatever choice you make is at least very good.
I've been seeing a fair number of Nehoni on Iron Chef as of late in addition to those listed by BDL. I haven't seen nearly as many Wusties, shuns or Mac's recently. It's almost a complete mixed bag of other J-knives at this juncture.