Living in the southern US, I have little experience with needing to dress with layers. However, in preparing for future travel, I'd like to have a mid-layer, and a jacket of some sort seems to be the norm. How would a down jacket compare to a shetland sweater? When I visited Europe last year, I typically wore a heavy sweater over a long-sleeved shirt, and it kept me warm enough, except in torrential downpours in Scotland, and obviously an insulated jacket wouldn't work well in that scenario, either. Which option do y'all prefer? Keep in mind, however, that my current question regards no particular destination; mostly urban travel but maybe some light camping/hiking...I mostly just want to be prepared.