Gah. Take a break for a few months, and come back to find this. Well, here's my two cents, for whatever they're worth. Please excuse any incoherency in this post - I'm not quite fully awake at the moment.
I do not see that there is anything inherently superior in either type of scenario. That said, there are variations in the difficulty of producing a good scenario of either type.
In a medium like BoA, linear scenarios will be easier to write well than non-linear scenarios. Quite simply, the non-linear scenario will require significantly greater scripting effort to deal with all paths the designer chooses to implement. (Note: Not all possible paths - that's not going to happen, unless you make a ridiculously small scenario.) Given this, and
assuming a designer equally talented in the production of linear and non-linear scenarios, more scenarios of a given quality can be produced in a given time if those scenarios are linear. Since I strongly prefer to have a greater variety of scenarios, I'd have to say that I prefer designers to produce linear ones.
(Note: The preceding assumption is obviously not true, however, it is my opinion that designers are generally better at making linear scenarios than non-linear ones. If you happen to be an exception, then by all means, make non-linear scenarios. Assuming that they really are good, I'll enjoy them just as much as the linear ones.)