These decals are printed on vinyl. Even though the original decals were not vinyl I believe there are several good reasons for using vinyl now.
Modern vinyl's are only 2 mil's thick, that's .002" or 2/1000's thick, which is thin enough to stretch over the compound curves found on the cowls of many motors. (See installation section)
I have over 30 sets of original decals and they were all made face down or in a sandwich between two layers of paper, (See picture). The decals were applied against the surface you wanted with the top paper still in place, rubbed down and then the top layer was peeled off. There was no "slide off" involved.
Most of the reproduction decals available in water release type are made face up so you have no choice but to slide them off the paper onto the desired surface. This is not a problem with smaller decals that are round or square with smooth regular edges. But if they are large like many of the side decals, (which can be up to 15" long) or if they have irregular edges like the Seahorse symbol on the front of the 1956 Johnson's or the side of the 54's, that have long thin pieces, it becomes very difficult to slide them off without tearing them. Also the thin pieces fold under and then tear off when you try to unfold it. This is probably the single biggest cause of frustration with this type of decal. They are extremely fragile.

The second biggest cause of dissatisfaction is incorrect or inaccurate artwork. For one thing using the wrong colour. For example 1955 Johnson decals were not white but cream, similar to the trim paint. (See sample) Also all 1956-58 decals that went over the cream paint were a reddish brown to blend in with the various shades of Holiday Bronze, not brilliant Fire Engine Red. (see sample) This picture shows a new old stock faceplate along with my vinyl decal and somebody else's decal.
The water type decals are made with silk screens. You must have a separate screen for each colour in each individual decal. I have done all the Johnson decals for 1949-1958 and am only missing about six decals. So far I have 225 decals. Some are one colour and some are four, so that would mean about 600 silk screens to do them all. That's a pretty expensive undertaking for a product with such a small market. This causes the manufacturers to cut corners such as offering one year's gas tank decal for all years and leaving off the tank capacity line so they don't have to make different decals for the two sizes of tank. It also causes them to make multiple pieces where one existed originally. For example, the lower cowl decals for the 1957 Johnson's looked like "Sea 18 Horse" in one piece. I believe that in trying to reduce their costs by limiting the number of silk screens they have to make causes them to send you those decals in four pieces which makes installation four times as difficult and you also have to mess around with the alignment.
All my decals come in U.S. and Cdn. versions where applicable and all my fonts match the original in width and height, (See example of a bad match). All of my decals are available for viewing before you buy. If you have something non-standard let me know and I will make up a set with whatever you need.
I have finished all the Johnson decals for 1949-58 except for about six I am missing pictures of.
If you have a good sample of a decal I do not have yet send me a picture and I will do it. See here for a sample of what I need to do the artwork.

So to sum it all up here are the reasons to choose vinyl
1-Correct colours
2-U.S. and Cdn. Versions available where they existed
3-Gas tank decals available for each year
4-Electric start box decals available for each year
5-All artwork is correct for each year and H.P.
6-All fonts are correct
7-All decals are one piece where the originals were
8-Vastly increased strength and durability
9-Ease of installation
10-Correct colour and style of carb decal included with each set where applicable.
11-Best of all lower cost.

One final note about "Water Release Decals", checkout this picture and you will notice that the words "solvent applied" are stamped on all three packages. Most of the decals for the 50's were not actually water release, but were solvent release. OMC used part # 277409 and Mercury used part # C-92-25143. It is a naptha based solution. I have soaked some of these decals in hot water for a half hour, changing the water every ten minutes and they would not release. Less than one minute of soaking in the naptha had them releasing just fine.