Note - this post has been heavily edited by Jeff H. ; anyone can read the sailing world links about the respective boats and judge for themselves.....WDS
Note- That is correct, this post was edited to correct grossly misleading statements made by WDSchock in violation of forum rules. Those edits have been noted. Jeff_H
The S30 will not (J_H)
sail better in light airs. The S-30 rates about 30 seconds a mile (slower J_H) than the J/30 (144 vs 174 in most regions, with a bigger spread in light air regions like the Chesapeake and Long Island Sound J_H). The J-30 is also a stable boat in heavy breeze, and will surf easily. The S30 hull is solid fiberglass, so no core issues there (except for notorious deck problems on the Santanas of this era J_H). Ask Newport Newbie about his S30. He posts here quite a bit. Or check this review http://www.sailingworld.com/sailboats/santana-3030
The J30 was built by a contract manufacturer called TPI (which is still in business after a name change which occured due to the retirement/death of one of the partners, and which is still highly regarded as one of the higher quality contract composite fabricators for a company which is also still in business and still uses this same contract fabricator J_H). This review (does not J_H) imply that the J/30 a pig in light and medium winds - but does say that it is excellent in heavy breeze. http://www.sailingworld.com/sailboats/j30
So - depends on the prevailing conditions in your location.