Ron Wanttaja wrote:
Years ago, when there was a controversy as to whether paddles or
propellers were most efficient for ships, the British came up with a
simple test: They built two identical ships, with identical engines,
one with paddles and one with a prop. They tied a rope between the
sterns, and had the captains go to full power to see which had more
thrust.

Wikipedia says that "In 1848 the British Admiralty held a tug of war
contest between a propeller driven ship, Rattler, and a paddle wheel ship,
Alecto. Rattler won, towing Alecto astern at 2.5 knots (4.6 km/h)...."

http://en.wikipedia.org/wiki/Propeller

However, it is probable that the paddle wheel ship simply didn't have the
right size paddles. Paddle wheels should be capable of efficiencies similar
to propellers - but it takes very large wheels.