Dr. Ross has a connection with one of the manufacturers, so he probably hesitates to give an obvious answer to one category of your question. I don't have any such connection, so I will. If you're interested in powered ships (as opposed to sailing ships, or powered small boats), there really is only one company currently offering a range of good ones: Bluejacket (www.bluejacketinc.com). There you'll find warships and some civilian ones (tankers, freighters, etc.). They have solid basswood hulls and brass and britannia metal fittings. I believe Dr. Ross designed most of them, and he most emphatically knows what he's doing. I don't have any hesitation in recommending any of those kits.
I think the only powered ships in the Model Expo catalog are a couple of versions of the Titanic from continental European manufacturers. I haven't seen any of those kits, but frankly, on the basis of the other products I've seen from those manufacturers (see below), I wouldn't buy one without getting a good look at it first. And I have to say that the wood-plank-on-wood-bulkhead system strikes me as a rather odd method to build a static model of a steel ship. But maybe it works well; I shouldn't denigrate those kits without examining them.
The wood sailing ship kit business is divided into two categories. Four fairly-widely-available manufacturers make genuine scale sailing ship model kits: Model Shipways, Bluejacket, A.J. Fisher (www.ajfisher.com), and Caldercraft (also known as Jotika). Model Shipways and Bluejacket are long-established American firms with fine reputations; they know what scale modeling is about. Some of their kits have been around longer than others, and therefore vary a bit in quality, but any of them can serve as a sound basis for a scale model. A.J. Fisher is an old American company that's recently been brought out of hibernation under new management. I haven't seen any of its kits in the flesh, but on the basis of the company website they certainly look good. Calder/Jotika is a British company whose products are hard to find in the U.S. I've never seen any of them in person, but they have an excellent reputation, which is confirmed by knowledgeable reviews in various publications. Jotika kits are quite sophisticated and, unfortunately, quite expensive. (The Jotika H.M.S. Victory is on 1/72 scale and costs about $1,000.)
I'm vaguely aware of a couple of companies in Germany and Northern Europe that, as I understand it, produce some excellent wood kits. These, unfortunately, don't seem to be distributed at all widely in the U.S. I can't claim any familiarity with them.
The other category is made up of what I call the HECEPOB kits. (That's Hideously Expensive Continental European Plank-On-Bulkhead.) Manufacturers in this category include the likes of Mamoli, Amati, Corel, Euromodel, and Artisania Latina. Serious, experienced scale modelers generally hold these things in contempt. They do vary somewhat in quality, of course - and I admit I've seen several really nice models that were built from such kits. Generally, though, they're characterized by shoddy research (if any), inaccurate, miserably-drawn plans, second- or third-rate materials, inaccurate, blobby fittings (which frequently get recycled from kit to kit, irrespective of appropriateness), and extravagantly high prices. Such kits may make nice decorations - and if that's what the customer wants, fine. But unless they're modified almost beyond recognition, they do not produce scale models.
There's one notable exception. In the past year or two one of the HECEPOB firms, the Italian company Amati, has started a range of British sailing warship kits under the label "Victory Models." These, I believe, are designed by a gentleman who used to work for Jotika, and they certainly give every appearance of being high-quality products. (They're listed under the Amati label on the ModelExpo site. The current range includes the sloop-of-war Fly, the bomb ketch Grenado, and the cutter Lady Nelson, with more promised.) Again, I can't speak from personal experience, but these kits look to me like good ones. They seem to inhabit a totally different planet than the HECEPOB trash that otherwise characterizes the Amati line.
If you do a search in this Forum under the word "HECEPOB" (for which I am proud to claim responsibility; if other modelers can invent words, like "TallShip," so can I), you'll find some rather high-spirited discussion of the matter. Some folks genuinely seem to like HECEPOB kits; I wouldn't have one in my house - let alone spend good money for it.
If you're interested in smaller vessels, Bluejacket offers several nice ones. Another good company in that category is Midwest(whose wares are shown on the ModelExpo site). Midwest kits are well-designed, with good quality materials, sensible construction methods, and reasonable prices. They make excellent starter projects for people new to the hobby.
Hope that helps a little. I have a feeling this thread isn't over; some other Forum members may well disagree with my recommendations. If so, great; that's what this Forum is about.
Good luck.