Granted, the F4U was a terrific performer, but it was extensively used as a ground attack aircraft in the PTO, not just by the USN, but also RNZAF and FAA, so its air-to-air combat figures are generally going to be lower than the Hellcat.
I can't really agree, since who would be operating it? The USN didn't have a great presense in the ETO and the FAA didn't use the Corsair extensively in that theatre. The USAAF certainly had its own performers, so while F4Us might have made an impact, I doubt there would have been a desire to spur development of it specially to suit the needs of the ETO. Its performance was that much greater than ETO fighters.