I can think of two reasons to chose a more modern lens: most are made with the popular 39mm mounting thread: the aperture scales on some older lenses tend to have unequal distance between detents whereas more modern lenses have equidistant physical step sizes. There is also the question of image quality, for the best quality work you want 6 element, one step down the quality ladder come 4 element units and the inexpensive varieties are often 3 element, see if you can find out which of these types the lens is.