I prefer a bolero for its versitility. Simply, I find arm warmers never stay up if you take them off and then have to put them back on for some reason. The bolero, you can take on and off a bunch of times, and they never ride down your arms and bunch up at your wrists. For touring I'd definitely go with a bolero.

I have some Pearl Izumi boleros with a zip front. Love 'em.