Richard,
At the time, I had not considered butyl tape, and had not done any research on it. The Dow Corning 795 had been recommended by two very experienced DIY'er friends who had been using it for years with excellent results.
Since then, I've done the research, and butyl tape looks quite interesting. It has almost no adhesion strength, but has a fantastic elongation factor (something like 5x to 9x!) without rupturing. I've come to the conclusion that in almost any bedding application that has its mechanical strength supplied by fasteners, and not by the bedding, butyl tape makes a lot of sense. Especially in places that tend to "work", like chainplate through-deck seals.
The one possible exception is where silicone has already been used on fiberglass/gelcoat. Fiberglass has a tendency to absorb some of the oils from the silicone, making it difficult to get a seal with non-silicone bedding materials. I do not know if this is a factor for butyl tape.
On the last project I did (rebuilding the two deck hatches), they had previously been bedded with silicone. I considered butyl tape, but chickened out and stuck with the 795 because its a silicone and is compatible.