My opinion is, that Mustang was clearly superior to T-bolt and Lightning. It's also backed up by datas. Normal P-51D was faster and much more turny than the others. Also duration was higher.
Also the US-Experts vote Mustang superior to P-47, P-38.
Also losses of Luftwaffe in Normandie were not that high, i had in mind for some years. Take i.e. June 1944 in France were LW lost ~800 planes and ~240 dead and missed personel losses.
http://feldgrau.slacker.se/wwiilexic...-m-fbottom.htm
Of course these losses were high, but not for breaking backbone.