A survey of preference may not say much, but it would be something. It would be more helpful to have data on Kindle page views per minute by text display choice, controlled for other factors like book, typeface size, etc.

My biggest problem with my Kindle is that I can't even get that sort of data for myself. I'd love to know when I read, how long, which topics, and so on.

I would guess that the default font is also the most used.