Wow. I'm lost on your thinking here. If you're wanting to be pretentious and look cool (is this a mid-life crisis thing?), go for the four-wheeled convertible. If this is a chick thing, go for the four-wheeled convertible or a bike for two (we call it a tandem). If you're going for sweat stains under the armpits or unsafe riding conditions, use the backpack. If you like to show off your common sense and intelligence, use a rack (or panniers, or basket).
Next problem, please!