Well sr801, someone here, and I'm too lazy to look back and find out who, mentioned the fact that unless we threatened a really important target, the Luftwaffe ignored us. Bombing Germany was something that couldn't be ignored. We lost lots of 4-engined bombers and their 10-11 crewmen that couldn't defend themselves as well as was thought. A cross-channel invasion would also bring them up except they'd have Spits and Jugs to fight.Fighting fighters is a lot harder and are more dangerous opponents. And, as I mentioned, most of the attrition factors would be in our favor.