Perhaps the answer lies in the two aircraft's longevity in service wth their primary users. The Jaguar flew in front line service for the UK and France till 2007, 16 years after the Corsair had been retired. To me, that says a lot.
I don't think that is the answer. In just talking about primary users (US Navy for the A-7, and RAF/French for the Jaguar) the dates may be interesting but do not tell the whole story.
A-7 first flight 1965, intial ops by front line squadrons 1967 and right into extensive combat service. Retired @1991 from the USN. Other users until later (2014)
Jaguar. First Flight 1968, intial ops by front line squadrons @1974. Retired by France 2005, RAF 2007. Other users still continue.
So by your reasoning the A-7 had about 24 years with its priamary user, the Jaguar about 33 year- so it is "better". Yes a longer service life, but that does not by default make it "better". Both had pros and cons for their designed role as others have pointed out. Great input from bomberh.
And why were they replaced and what were they replaced with? The A-7 was replaced by the F-18 which was designed specifically to replace it, and by 1991 the hornet was mature and ready to replace the tired A-7's. The Jaguar was replaced arguably by nothing in RAF service and the Rafale in France, which was not in service until much later. So did they last longer because they were "better" or because there was nothing to really replace them with?