Traditional all the way
I've had my traditional Cat 27 for over 13 years, and before that had a Coronado 25 (another "Butler boat") for 15 year that had a dinette interior. I've also sailed fairly frequently on a 27 with dinette arrangement. The problem with the dinette is the fact that you only use the table occasionally, yet the thing takes up almost half the cabin all the time. Any time you want to go up to the V-berth or head, it's in the way. My head is rarely used, so I store my inflatable dinghy in it's bag there. On a dinette, I wouldn't be able to get it past the table. The table edges on a dinette are dangerous in a seaway compared to the soft cushions of the traditional. Also, rail handholds on both sides of the ceiling on a traditional fall more easily to hand when you hit a big wave than they do above the dinette. And the dinette is really crowded for seating 4, while the fold-out traditional table, while still snug, is much better. (In either case, you better be young and supple.) Stowage cubic ft seems to be about the same, but the long compartments under the berths in the traditional seem to be more usable than the short ones in the dinette. If you plan to race, you need the openness of the traditional interior to haul around sails, pack 'chutes and such. If you're looking at a dinette one with galley opposite the dinette rather than in the port aft corner of the cabin, you'll find that it gives you almost no counter space (unless you consider the dinette table a "counter"), less headroom over the stove and icebox, and much less ventilation from the stove. With either, you can install a fold-down counter extension over the berth in front of or behind the galley that almost doubles your counter space, but it's more convenient to the stove in a traditional. When necessary, I can use my fold-down table as a chart table (you can a full-time dinette also, but the dinette encourages you to sit down to navigate, which, makes you less help to those driving. The assertion that the dinette becomes a double berth just is not true, if you & partner both have any hope of actually sleeping. And the best reason, if you install the LCD TV and DVD player on the portside, just aft of the main bulkhead on a traditional, it's easily viewable for up to 3 people sitting on the stbd. side settee. Try that on a dinette!The key issue is less space to move around below.