Originally Posted by sivat

Road bikes have horizontal dropouts (I'm assuming you meant horizontal instead of vertical. if not, you have a whole host of other questions to be answered) because, among other reasons, it allows you to quickly and easily remove the rear wheel to fix a flat. On a track bike, if you get a flat, your race is over, so the speed doesn't matter as much. The older road bikes also used horizontal dropouts to fine tune the handling of the bike. Placing the wheel at the rear of the dropout gave for a smooth, mellower ride, while putting the wheel at the front of the dropouts would raise the bb slightly and make the bike handle and sprint a bit more quickly. For a commuter, I FEEL, that horizontal dropouts are better. Its easier to change a tire, you can run fenders and still remove the tire without removing the fenders, and if you go with a single speed, you can move the wheel and the brakes will still line up.