sans-serfi to serif
I prefer serifed type when laying down large sections of type, because in those instances, legibility is (to me) the most important factor. I've been told (and I find the argument compelling) that serifed type is more easily read because people read by associating the whole form of a word with the word, and not by parsing each letter individually (when one sees the word apple at a glance, perceiving a rectangle 5 units wide, with a 1/2 unit jut from the buttom where the p's are and 1/2 unit jut from the top where the l is the most immediate input to the read- and not seeing "a", "p", "p", etc.) Serifs enhance this effect by adding more information to the form, via micro-undulations to the outline of it. Even if this were not truly the case for human perception, I find the notion of perceiving words as shapes, of characters as detailing of those shapes, and serifs as detailing of those letter shapes appealing.