Define 'superior'? Breakdown of what we saw and heard in the film is as follows:
Nine confirmed Imperial ships versus fourteen confirmed Rebel ships (from dialogue and onscreen evidence), at least in that portion of the battle we were following. Of those, eight standard TIEs and eight verified X-Wings. Good balanced numbers for an experiment. A surface explosion took out one Rebel ship before the Imperial fighters even deployed. Vader alone took out six Rebels and a partial. I won't count his, as his ship wasn't standard. Han took out one Imperial. A second involuntarily suicided (evaded into Vader's ship, and spun into the trench wall). So we won't count those, either. Two Rebel fighters present were not confirmed X-Wings (Red 7 and Red 9 had dialogue or script references, but no models built). Those fighters were then conveniently taken out off-screen, as there were only six ships in the squadron when Red Leader made his run, all X-Wings. Luke's element was flying cover for that run and were still flying evasive due to the surface guns, but we saw no Imperial fighters attacking them or taken out by them. The Y-Wings we saw were not involved in the dogfighting. Three made the first trench run and were flying purely defensively. One was randomly there as Luke, Wedge, and the Falcon booked it away from the station, and may or may not have been part of Red, as one of the otherwise-unseen files.
So, the best we can take from eight for-sure X-Wings versus eight for-sure standard TIEs is: Two observed Rebel kills and two observed Imperial kills and a partial. All others were either other ships, which invalidates the data, or happened offscreen, so we can't know which ships were involved with which. In terms of final raw numbers, zero of eight standard TIEs survived the battle (unless those last four cut and run, which seems unlikely), and two of eight confirmed X-Wings survived, but with damage. From a numbers standpoint, that's more like parity than superiority, even given how external factors skew the numbers (four of eight X-Wings taken out be sources outside the measured factor, two of eight TIEs taken out similarly, and it becomes six TIEs to four X-Wings). But there is still an error margin, due to other factors. We do not know for sure what type of craft Reds 7, 9, and 11 were, or what took them out -- if, indeed, all were.
