Charles, I sympathize with your agony (angst?) over the 34 vs 35 decision, but maybe you're worrying too much, or about the wrong things - at least, I'm pretty sure there is no simple answer.
We have people here who are perfectly satisfied with the sound they get from a low B on a 32 scale instrument (you might find some old threads by searching). Personally, I think by the time you get to a string that heavy, you should have at least 34, and 36 wouldn't be a bad idea.
In deciding what I wanted to do, I actually calculated the string tensions for a few different string and scale lengths, and an inch (or two) really does make a difference.
Nevertheless, I don't think you should consider the choice between 34 and 35 as a make-or-break issue. I would personally be a little skeptical about going down to 32 for a five string, but I think the odds of hearing a big difference between 34 and 35 are negligible - as far as the instrument itself is concerned.
There are other factors that are likely to be more important: your choice of strings, amplification, and most critically, your playing style. Regardless of the scale length you decide on, you might have to baby the B just a little, maybe pluck it closer to the bridge or with a little different attack, to get a tone as similar as possible to the rest of your strings.
If all these things are working together, and otherwise identical, I seriously doubt you could hear much (if any) difference between a 34 and 35, at which point your decision should be based more on comfort. I'm not exactly a huge person, but even playing fretless I don't really notice the difference between 34 and 35.
(My 5 string Alembic is effectively 35.5, and while I also have a 34 4 string strung BEAD, it's not an Alembic, so I can't make the direct comparison you are looking for.)
I guess my advice would be this: if you think you can physically handle the length, more is clearly better (although here you can also run into other odd problems, like a smaller selection of strings!). But if everything else is in place, it's very hard to believe you would be dissatisfied with a 34.
-Bob