I have a cousin with a 1976 T-30 and a friend with a T-27. The 27 will definitely feel small compared to the 30 but is still a viable offshore boat properly equiped. The 30 will be a more responsive, faster boat and perhaps mroe fun. One thing to consider is the tankage. Both were originally equiped with the Atomic 4, but as an option on the 30, a UNiversal diesel was offered. There are two layout for the 30, one with a mid-ship galley on the starboard and the other with an aft galley. My cousin has the midship version and it's OK, but I think I personally like the aft version.
Just like most S&S designed boats of that era, both will heel to a point, settle in then start Smokin'
Oh, by the way, I just rebuilt my cousin's rudder which the inner metal tabbing broke (corroded) away from the rudder post, so this may be an issue to look for. I fabricated the new skeleton out of a better grade stainless than what Tartan used.