In my opinion (but the number of answers is limited), the option "both" is really missing. I like to think I'm not the only one that like a print copy for "couch potato mode" reading, an epub to read on the go, and a pdf to search later in (in my experience, I haven't yet found an epub tool where search is as efficient than in pdf tools)
So I'd really choose the "give me all of them" choice ;-)