We race our 275 regularly against 27s and super seals. Overall, they are all fairly well matched. We have found that the 27 and super seals are better up-wind and the 275 is better down-wind (although this may be partly due to our roller reefing).
Unfortunaterly we have the only 275 at our club and so have no other 275's to test our performance against so it would be great to know how others find the 275 compared to the 27 and super seal.
Tom