There are four major worldwide international catalogs (plus several smaller single area specialized catalogs such as Facit for Scandinavia and Zumstein for Switzerland, which are only issued for their home countries and whose publishers have no worldwide versions of their catalogs). German philatelists collect their stamps by the Michel catalog, which publishes a worldwide catalog in German, along with a highly specialized catalog of Germany and area. Yvert is the French catalog which does substantially the same thing for francophones, again with a specialized France and Colonies catalog. Gibbons is published in Great Britain and once was a worldwide catalog, though their most popular yearly offering is a British Commonwealth catalog that is the standard for collecting the former British Colonies. And in America, we have the Scott catalog, published every year in numerous (costly) volumes. It is only a matter of time, perhaps even in less than a decade, when the last of the annual catalogs are published, and all catalogs and their updates will be found online. Each of the four major worldwide catalogs have their strengths and weaknesses.
Michel is the world’s most successful catalog in terms of printing profits and number of users. It helps that Michel is printed for the enormous German stamp market, but philately, at least the way most collectors collect today, is really a German invention. The Michel catalog has several unique factors about it that make it fun to use. First, the set up for perf varieties is far easier to use than Scott. Michel uses small letters after the number to designate varieties, as does Scott, but there is a consistency in the listing and layout that make cataloging perf and watermark varieties far easier to find in Michel than in any other catalog. Additionally, the Germans love their booklets and booklet panes and list, for nearly every country, extensive booklet and advertising combinations that no other catalog touches. There is a compelling logic about the Michel set up, and most worldwide philatelists who have had experience with all the major catalogs find it the easiest and most appealing to use. Of course, the Michel Germany and Area catalog is without peer, listing hundreds of thousands of varieties in a couple thousand pages and making even the most complex area of German philately approachable.
Yvert does not as good of a job. The worldwide catalog suffers from production delays—volumes are promised and then never come—and the French specialized catalog lacks the consistency of what the Michel brand does for Germany. But the Yvert French catalog lists many specialty items not found in any other catalog and is especially good for imperfs of twentieth century stamps. Thirty years ago, Yvert published a masterful nineteenth century catalog which is still in print and which, if you read French, is a marvelous and coherent explanation of what can be done with classic French philately.
Gibbons is a very good catalog, but it suffers from some meaningless specialization. The catalog is good with the colonies, and the varieties that it lists are popular and well worth knowing about, especially as they can often be found in American dealer stocks being offered as the most common variety. But the Gibbons listing for Great Britain is so overspecialized and arcane that it is often useless. The copious shade listings on the 1902 Edward VII are the best example. Numerous shade varieties of the same stamp are listed with vastly different prices where the description of one shade is the equivalent “red-brown 50p or brown-red 50 Pounds” Such small differences are impossible to describe in the catalog text, and Gibbons has page after page of such listings that are collected by few people because they are essentially meaningless.
Scott, the American catalog, overall is pretty good. As American collectors and dealers, we hear a lot about what Scott does and doesn’t do. In the last twenty years the catalog editors, first under James Kloetzel and now under Charles Snee, have made a consistent annual effort to improve the catalog. Each year gets better and especially worthwhile is the Scott worldwide nineteenth century specialized catalog. Scott is the only one of the four international stamp catalog publishers to publish a catalog of this type. The catalog attempts to publish much of what is in the best specialty sections of each worldwide national catalog. The Scott Worldwide specialized is expensive, but you don’t need one every year, and it is even available on an iPad app.