A two wheel trailer is going to be more stable and easier to ride in that respect. However a single wheel trailer is going to be a fair amount faster. Think about it, there is much less weight involved with a single wheel trailer. Then there is only 1 wheel, half as much friction as there would be with a 2 wheel trailer.

So 2 wheel trailer=more stable and able to handle larger more unstable loads but weighs quite a bit more and has more rolling resistance.

A 1 wheel trailer=lighter and much less rolling resistance which means much faster however it would be best to use lighter loads and less wide loads.