My first comparison between O30 and ssc27 is the design, I got really bruised and abused single handing O30. I'm sure better sailors than me can manage just fine, but I just enjoy the space in the Seascape cockpit.
And then there is the a-sym, so I don't have to do a trip to a bow every time I try to jibe.
In light air O30 can be a fast boat, I don't have a massive genny on the SSC27, but the boat is overpower as it is so unless I find 5 friends to seat on the rail it would be hard to carry more sail.
They are both really light and fun boats,