Doohickie

I think I was the one that made the remark that inspired this thread. When I first started commuting on my bike, I got a trunk bag. It is enough most of the time. I typically pack a change of clothes (not including shoes), personal stuff (wallet, badge, phone, keys), bike lock and a lunch. No problem for the trunk bag. If I need to I can attach the pants to the top of the bag with the built-in bungee cords.

However, as the weather gets colder/wetter, and I'm riding to work before light, add in reflective fredvest, maybe even rain gear, extra layers of clothes to keep warm, gloves, etc. I wear them to work but usually dress much more lightly for the return trip so all that stuff has to get packed on the bike. Usually, a single pannier does the trick; it holds a lot more than my trunk bag, and they are built to be more expandable than a trunk bag is. But since I have a pair, I use one side for clothes & bike lock and the other for lunch/personal stuff. Also, if I have to take anything extra, it's easy-peasy with panniers, but next to impossible with the trunk bag.

I prefer the panniers, not only because they hold more, but because they sit lower. The bike feels better ballanced. Also, the blinkie I have that I clip onto the trunk bag, well the loop on the trunk bag allows the light to sag down and not point straight back. If I use panniers I can attach the blinkie to my saddle bag where it sits in a straighter position (that is not visible if I use my trunk bag).

So there ya go. Probably more than you wanted to know.