Comparing Wikipedia descriptions, the Shannon class are composite compared to aluminum construction for the Coast Guard’s 47 foot MLB. Displacement is lower (14.6 tons vs 18 tons). Length is slightly less (44’7″ vs 47’11”). Beam is slightly greater (14’11” vs 14’0″). Draft is less (2’6″ vs 4’6″). Speed is slightly higher (27 knots vs 25). Range is up (250 vs 200)
As reported in the Wikipedia description of the class,
Most Shannons are launched by a newly-designed launch and recovery system by which a tractor propels the lifeboat on its cradle into the water. The cradle is then tilted and acts as a mobile slipway as the boat is launched by release of a single chain from the wheelhouse, rather than the old carriage launched method of four chains being released by crew members on deck. Recovery is bow first onto the cradle, which then rotates through 180 degrees, enabling the boat to be launched again within ten minutes. Some Shannons will be kept afloat at moorings or a pontoon berth and the boats are also capable of being slipway launched, although only Swanage currently has a slipway launched Shannon. The boat at Workington uses the same unique davit crane system as the previous Tyne class boat.
Thanks to Lee for bringing this to my attention.