^ good summary of the pros and cons of each way. I have panniers and handlebar bag on my commuter and tourer, and use a backpack when I take my fixed gear to work. Each method is right for the type of bike.

I like the roominess of dual panniers, when I need to haul extra stuff to/from work. Also, the feeling of freedom from extra *stuff* on me.

I like the zippiness of my fixed gear without the odd weight ballast of panniers and a handlebar bag. It makes me want to ride with a bit more agility. Although, the backpack is sweatier, and it's not easy to get into quickly, unlike the convenience of a handlebar bag.

But in the end, I'm not faster or slower with either one. It's a matter of preference. I'm glad that I can choose on any particular day.