One vs. Two wheeled bike trailers I am considering making or buying a bike trailer.  

It seems to me that the most important desision I need to make is whether to have a one wheeled bike trailer like the Bob or a two wheeled bike trailer.  It seems to me that both have their advantages.  Does anyone have any reason why one is preferable to the other?  

One wheeled bike trailer (Bob trailer): 



Two wheeled bike trailer:
One-wheeled trailers are more agile and don't increase the width of your bike.  They lean with the bike. If you're going to go really narrow places, you need one-wheel.

Two-wheeled trailers can generally carry more weight and are less prone to making the bike fall over when you stop.

So, what are you going to do with the trailer?  Going up and down mountains with narrow trails: get a one-wheeled trailer. Carrying 50kg of equipment from the hardware store home using streets and wide paths: get a two-wheeled trailer.