A contrary opinion
I have never measured cushion length between the c27 & c30 but i have owned a C22, C25 & now C30 & the difference between the C27 & C30 is more then measurable.
The C27 is a fun & responsive boat. I do not feel that there is much difference in maintenance costs, as all boats cost $$ to maintain. I would not buy a boat for how many people the cockpit will hold, but for the pleasure that the boat gives YOU & your first mate. That said, I have never heard a sailor regret buying a boat a lil' bigger, but plenty of gripes about one being too small. The C 30 has standing headroom for a sailor over 6 feet. Its beam is 10 feet 10". it weighs considerable more then a C 27 with weight at 10,000 lbs. empty, or over 7 tons. Weight in the hull & keel = comfort & ease of moton under way, as does a longer water line. I can completely stretch out on the seats of the C 30 with room to spare. 6 would be the max I would want in ANY cockpit. I do rather enjoy sitting behind the wheel of the C 30 facing FORWARD, without twisting my body on a bench seat, as the C 30 bench runs acroos the stern for better ergonomics. This does matter as one ages.
As the former owner of tiller boats, there is no comparison between the comfort & ease of wheel steering & the wear that a tiller has on the body after 4-6 hours of fighting that stick. Once U sail with a wheel U will never go back to the archain tiller. If U have the budget then go big with the C30 & U will not be disappointed. It is the biggest 30 footer ever made in terms of cabin & berth capacity. But if the C27 is what U can afford, then its better to sail something then nothin! They are both good boat designs. But don't buy a boat for how many people it will hold. Sail both boats, & let them speak to you about there pluses & minuses. Cheers.
I'm going to present a contrary opinion to some of the above.
A year and a half ago I sold my 1987 Catalina 30 MK-II and downsized to an Ericson 26-2. While I liked many things about the C30, I decided that it was more boat than I needed, especially because I tend to singlehand a great deal.
For me, anyway, the Ericson 26 is a much more fun boat to sail. One of the things I disliked most about the Catalina 30 was the wheel steering. This is not a criticism of the Catalina's wheel steering in particular--there was nothing wrong with it as such--but rather a statement of my personal dislike of wheels. I've never found one that I liked. I really tried to warm up to it, mind you, but in the 8+ years I owned the boat I never cared for it. I found sitting or standing at the wheel uncomfortable for long periods of time. I much prefer sitting with my back against the cockpit coaming, bracing my foot on the opposite side of the cockpit, and steering from that position. The ergonomics just work better for me, at any rate. I found with the wheel that I was frequently changing positions to remain comfortable, whereas with the tiller I can stay put for much longer with greater comfort, given the back support and ability to brace myself with my foot. The tiller also puts me in the forward part of the cockpit, in a good position for operating the traveler and other lines led to the companionway.
Provided that the boat has a light helm--as my Ericson 26 does--then I find it much more enjoyable steering with the tiller. The tiller gives me a better "feel" than a wheel, which tends to insulate me from the helm. However, a boat with a heavier helm, such as a C30, really needs a wheel for the mechanical advantage; I think that boat would be a bear to sail with a tiller. But it's pure joy to surf down the side of a swell, bombing home from Isthmus cove on a broad reach, when steering with a tiller on a boat like the one I presently own.
Anyway, I'm not trying to kindle a "tiller vs. wheel" war, and to those who prefer wheels, I say, "Good on ya!" But I do object to a blanket statement like, "once you sail with a wheel you will never go back to a tiller"; that has certainly not been true for me. For me it's quite the opposite: If it should turn out that I want to get another boat someday, I'm quite sure I'll do my best to avoid getting one with a wheel--or at least one that cannot be readily converted back to tiller steering. But again, that assumes a boat with a nicely balanced, light helm.
As for the C30 generally: It's a great boat and I'm glad I owned it. While I enjoy sailing my present boat more than it, the C30 does not have any glaringly bad sailing characteristics. It's a good, honest boat with a fantastic interior for a boat its size. I cruised mine to Ensenada and found it very comfortable with three of us aboard. I've done shorter trips with four and we still remained friends. I think they are reasonably well built and there is excellent support, both here and especially on the Yahoo Catalina 30 list. It's certainly worth considering.