Oh, I don't think it's preferable. I just don't think it really matters. At least not as much as people who have never tried it think it does. I've heard over and over again "Oh, I could never read from such a small screen." But only form people who've never tried it. Anyone who has tried it says "you know, it's really not a big deal." And I think (Ann mentions this, too) that the brightness and sharpness of the iPhone screen is actually more pleasant to read than the slightly grey and matte appearance of the Kindle. But you're probably right that this is more personal preference than anything else.