The Hylas and Stevens 47 are the same Sparkman & Stephens design built by the same yard in Taiwan, Queen Long Marine. Queen Long hired S&S to design the 47-footer for them right around 1981. Bill Stevens of Stevens Charters imported most of the original hulls, and they named her the Stevens 47. Later Queen Long Marine rebranded her as the Hylas 47 along with introducing other Hylas models.
The real difference between these two is the rig. The Stevens has a beefier rig. The Hylas 47's are high quality as well but just a little less robustly equipped. These Stevens models have become cult boats and rightly so.
The performance of these whether Hylas or Stevens is legendary. The hull shape and keel-rudder configuration make them surprisingly stiff and fast boats, well-balanced in any condition. A Hylas 49 model with a raised sheerline and sugar scoop stern is the current evolution of the 47.