Many thanks for the comments and the well-founded thoughts!
Well, one part of me would prefer The Adventure Island since it would perhaps give me access to slightly longer trips (in suitable winds).
Edit: and it would be more stable in tougher weather.
I'm sometimes participating in various local environmental projects (like sea bird inventories) and such. So it would be nice to combine kayaking with those "tasks".
Anyhow. There is always a question of various aspects (price tag not the least) and smaller compromises.
The Revo 16 is most certainly capable of assisting me during those trips as well.
I only consider the use of slightly different muscle groups (Peddling vs. cycling) as a positive feature. It's the same between my traditional race bike and my recumbent velomobile as well. I think it was mentioned somewhere, that the difference in muscle use is around 10% between the two (if one tries to put a percentage to it). It took about two months before I felt that I could have the same efficiency in the recumbent as on the race bike. But I haven't felt that I've lost anything when switching back to the race bike even if it has been unused for a long period. I don't have to get used to it again. On the contrary, i have the impression that I'm even stronger on the race bike than before. Perhaps due to stronger support from those muscle groups that are secondary (but still important) during a specific form of practice. But now I'm only speculating...
Regarding sailing, I have had exactly the same thoughts when it comes to "safety" - in other words: yet another method to propel the boat forward if other things for some reason fail.
And by the way, My assumption that the Revo 16 might be a bit more uncommon "out there" was just a loose suspicion based on me not finding as much "owner reports" or reviews about it as for some of the others. But I haven't counted search hits either - I just had the impression that any other Hobie Kayak shows up in greater numbers even when searching for the Revo 16.
And I didn't interpret that as something against the Revo 16 - that it would be unpopular or something. The reviews I've seen have been very positive.
So mentioning it was, from my side slightly, unimportant.