Adam,
Knowing a little about the types is useful sometimes. (Like the above guys mentioned, it kind of tracks when Stanley made changes to the planes, each time a noticeable change was made, the type # was advanced one unit, for example Rexmill says the Type 15s were made from 1931 to 1932, and the type 16 was made from 1933 to 1941.) You can identify the plane by Type # and then know a lot about the frog design from that, with out taking the plane apart, something that is worth knowing if you buy planes on Ebay, like I have to.)
There are limits to this, because as was pointed out above, the Type # was not something Stanley came up with, the type # listing was something collectors and users came up with LONG after the fact. Thus when Stanley went from one type to the next in the series, they used up all of the parts for the previous type on the later type, when they fit, so you can have parts from more than one Type # on the same plane, and Stanley made them that way. Also, when parts got lost or broken on a plane, the owner would come up with a part that fit, either from another broken plane or buying a replacement part from Stanley, so there are a lot of Frankenplanes out there.
In the case I listed above, the frog design of the type 16 was not quite as good as the type 15 and some of the earlier frog designs. Personally I like the type 10s to to type 15s, and can be happy with any in that range.
Jim can easily adjust the earlier types, so he likes them, but I have trouble with adjusting the earlier models, so stick with the type 10s to type 15s. As Jim mentioned above he also changed some of his planes to resemble the type 11 with a low knob, but he likes the large adjuster wheel of the type 12s and later, so he changed that feature out on some of his earlier planes. If I got a great deal on Ebay I would do some of the same things Jim did.
By knowing a bit about the plane types you can pick features you like, as Jim Mentioned, and modify existing planes by adding parts you really like to make convert a plane to a Frankenplane that has the best features of other types.
At any rate, it is worth the time to take the link to Rexmill that is listed above, IMHO.
Regards,
Stew