Personally I'd expect that the Golf has slightly better interior quality. My Exeo I had a few months ago had slightly better interior quality than my 17 plate Leon. More soft touch plastics, nicer material around the door cards and roof lining and I believe it had less road noise. Well better sound proofing more likely. This is what I would expect of the Golf vs Leon. Saying all that the Leon's interior is still very good and seems well put together. Much much better than the MK2 Leon.
Your Exeo would be way above the SEAT norm build/trim wise as it was a discarded Audi model - maybe B6 platform. I bought a VW Passat B5 new back in 2000, it was a very well built car, and I thought initially that that was due to it being a VW, I think that I was wrong, most of its good qualities were due to it being basically a mix of slightly older Audi B5 A4 with some S6 bits thrown it, but it was a good car. When I compare that car with my wife's bought new 2002 Polo, I could see that that Polo was a bad car for one reason, it was just a Skoda Fabia with some better trim and some extras, a complete dog of a car and a wallet raider from about 4.5 years onwards.