I would have originally said yes, but I've been riding my 20" folder for a while now, and find it just as good as my 700c tourer. The ride is different, slightly more responsive, my not massively so ( I was riding no handed, yesterday), and curbs, though not potholes, are something to be taken with more care (I have added 20x1.95s though).
Of course, I cruise at about 10mph, and never really exceed about 15mph, so the answer would be maybe different if I were looking for real speed (though I've read that that is debatable).
As far as I understand it BF's need some disassembly to fly with. I imagine they would need equal disassembly for a 24"BF, if not more, so you might as well get an Airnimal. Commuting and train use might be different, though I imagine the package wouldn't be as compact, and so might lead you to wish you had a 20".
I suppose for me, it boils down to the fact that I've found the ride to be just as good on a 20" as a 700c, and so I can;t see that a 24" would make any real difference other than increasing the size of your folded bike, and making it more difficult to pedal (rotational weight - or whatever its called).
Prejudice to 20" bikes is another thing entirely. I must admit, I was a little concerned that I would get looked down on for my "kid's bike", but then again, I enjoy the ride so much, I don;t really care.
As someone else noted, perhaps BF should just save R&D money and market their bikes as cool and funky. I honestly think that Dahon succeeds not only because of its pricepoint, but because it markets its bikes not just as practical but with a certain urban flair.