In my experience, the backpack question is hard because backpacks incredibly bother some people, and are uncomfortable immediately, and don't bother other people in the least, even after hours of use.
So if you ask someone who is bothered by packs the question, they can't imagine why you would want one when other choices exist. If you ask someone who isn't bothered by them, they don't comprehend what the fuss is about.
In many cases, a blend of both is a nice solution. This is how I packed the bike for 2-3 days, and still had my Osprey pack. The Tangle frame bag is new, and will be used exclusively (no backpack) for commuting this year.
