Sans serif is more readable (at least accrding to studies) probably because of much more coarser resolution of ye olde displays (~96 dpi vs at least 200 dpi for newsprint). Nowadays, no-one currently has conducted a rigorous study to determine whether it still holds true on Hi-Res displays, and whether the active lighting of displays will be different to the passive lighting of paper.
Is that true? Aesthetic is subjective. And for legibility, I always heard that serif is better for print, while sans serif is better for screens.