Either Sabre is a good choice. We have a 35 C&C k/c. I also am in the northern Chesapeake in Rock Creek on the Patapsco. We venture everywhere virtually within a weekend of here regularly. 5 feet would not be my deepest draft window....I would go more for 6. We have a keel/ centerboard which gives great flexibility. Some Sabres/ Tartans and C&C have this in some models. It offers the flexibility of the shallow draft feature with good pointing ability and the stability and ability to reef later when the wind pipes up. Given the choice I would go for the larger older Sabre if it surveys well. The extra comfort of the 4 feet length and inches on the beam makes a huge difference as does the weight in heavier winds. Most Sabres are quick well constructed boats with top end rigging and winches.
Also it is hard to beleive a 30 MKIII will walk away from a 34 MKI in any wind as the phrf rating of both boats are the same. I imagine that the sailor on the 30 is more adept than the 34. If abilities were equal the opposite should happen. As the wind increases the 30 will need to reef sooner if for no other reason than the centerboard down will give the 34 greater righting moment.
well, truth be told i have been sailing quite a bit longer than my b-i-l, and as such am able to tweak a little more from my boat than he can.
the major differences in the boat (aside from the 4' )..his cockpit is larger, and his head is more spacious (very welcome when you are decked out in foulies and have to hop on the pot...
i also have an unfair advantage;i have an asymm, he does not, so in those light air days, well, that's where i can walk away from him..granted, going downwind, he can pull his board up and gain back some advantage.
i would not however trade our engine access, my steps pull completely away, he has to contend with a less desirable set-up.
without going to the sabre site, i think our beams are identical, although i could be wrong (won't be the first or last time)...
bottom line, if you can find a well maintained 30 and it fits in your budget, snatch it up..