Style
Fractional rigs come & go with popularity. In the 60's, the many CCA type boats had fractional rigs. Masthead rigs became more favored under the IOR rule, because large mains were penalized and boats needed sail area somewhere. Despite overall trends sometimes the balance of a design simply calls for one rig style over another. The Tartan 33 and Tartan 10 have fractional rigs, for example. Masthead rigs are deemed easierr to sail because you can't do much with them. Fractional rigs are supposedly more difficult because there is more that you can do to adjust mast bend (and therefore sail shape). Theoretically, a fractional rig is more efficient going to windward because of the interplay of the jib & main, and the vortices generated by their relative placements. Right now, most of the current J/Boat crop (J/109,etc) is fractional. Fractional rigs might be seen as more sporty, like a standard shift in a car compared to a masthead rig being more like an automatic.