I commute on a number of bikes (because I have a number of bikes) and when the weather is nice and not cold ands snowy (as it is now) I prefer riding my road bike / commuter which is a fixed gear or my cross bike which is a gearie.

My road bike runs a 28 in the rear and a 25 up front which makes for a better ride as well.

Both bikes are quite fast and the cross bike gives up a little in the speed department but is better able to handle potholes and is more comfortable / plush although I could ride the road bike all day with no worries.

I average a little more than 30 miles a day in good weather as besides my commute I also live car free and all my getting around is done by bicycle.