Can't find it but found Smallfurry comment about the comparison of each groupset;
You cant really compare them directly, especially now that Campag have added more groupsets. It might be something like the list below, but then I've just pulled that out of the air, with little logical basis. I cycle around the in cold of Norway wearing shoes and clothes designed in the warmth of Italy. So I cant really lecture folk on taking the practicle option. but I'd say decide which of the main three manufacturers you like best in terms of fit and function, and buy the best groupset you can afford in their range.
Can't find it but found Smallfurry comment about the comparison of each groupset;