I just moved up from a 1978 H 27 to a 1982 H 30 and while they are both great boats the difference between a 27 and a 30 is pretty significant. On a boat size increases at about the cube of the difference. A 30 is almost 30% bigger than a 27. Both are seaworthy but the 27 is really an over nighter and when the weather pipes up the 30 feels much more substantial that is safer. ON the 27 you'll feel pretty vulnurable. If you know what you are doing both will see you through.
The 27 is much easier to single hand and you won't feel too overpowered if you reef early. The 30 needs to be set up with all the lines runningg into the cockpit with rope dlutches and with the reefing set up in advance. And again furl early. I single hand almost exclusively and when it pipes up on the 30 with the tall rig version that I have it pretty lonely out there.
On both you'll need a rollerfurling on the jib and I wouild recommend and auto pilot or tiller pilot on both. Also a charplotter and accurate depth sounder either stand alone or in the chartplotter/fishffinder is pretty important. VHF radio, Cellphone and do forget the FM if you are alone to sing along with. AM is you like to argue and the talking heads....
The 30 is more complicated to run and you'll need to be more careful where you drop the hook due to the depth of th keel. Getting pulled off the mud is a 27 is no big deal. On the 30 not so...If you'll be near the coastal US get boatus or seatow insurance.
The 30 is more liveable than the 27 but both will do you if you're carefful, perepared and watch the weather.....
Good luck, let us know what you decied.
