Originally Posted by exavid
Friction drives are simpler to install but do wear tires faster and tend to slip on wet roads. They do have the advantage of being able to be lifted with the clutch lever so there's no drag when pedalling. They do take up the space where saddle bags or a carrier would go. There are riders who prefer chain drives and those that like friction drives.
I had a TAS Spitz (Bike Bug) and it never slipped once set up properly. The old guy (80++) I got it from used to ride it on the trails in his woods, no problem. If you do go with one, use a 2.25 tire, and follow the manufactures suggestions for pressure.