I've sailed on 30's many times, and have cruised with, and raced against them as well. The 310 with the wing keel will be out sailed by the 30 TMBS in typical light air Chesapeake bay weather every time (unless the other crew really screws up). My 310 with wing keel, fixed prop, and roller furling rates 186 here while the 30 TMBS fixed prop roller furling (5' 3" draft versus 4' 4" on the 310) rates 189. The 310 is a great cruising boat, and I love the layout with the forward berth. We moved up to the 310 from a cata 27 I had for 15 years. In hindsight, I wish I had gone a little larger, but at the time the smaller size "couples boat" layout appealed based on less bottom surface to paint (and dive on during the season), slip fees, etc. The performance has been disappointing compared to the 27 and also a 34 which races locally.
dave