I agree that a single carrier was unlikely to have affected the outcome overall but in particular the land battle. however, the invasion relied on seaborne attacks at Khota baru and also within siam, at singora. There was another overland force advancing through Bamgkok, but was several days away from engaging the British in Malaya. these several days of delay were critical, as if they had been given, the Indian III corps may have bedded down better in the northern provinces.
British defence was centred around the aggressive use of Battleships Prince of Wales and Repulse, to get in and disrupt the invasion forces as much as they could. they never got close to doing that, because of a lack of aircover. that lack of aircover allowed roughly 60 G3Ms and a handful of G4Ms, themselves completely devoid of fighter escort, to deliver textbook attacks on the Britishs battlewagons and sink them. The issue of whether British Carrier fighters were superior or not isnt really relevant. Its more relevant to compare the performance of the british Carrier fighters of HMS Indomitable to the performance of those G3Ms and G4Ms. From memory Indomitables CAG was 22 Sea hurricanes, 12 Martlet IIs and 16 Albacore Night strike torpedo bombers. whether or not those 34 fighters could save PoW and the Repulse is certainly arguable. Whether or not Fce Z could have stopped the ivasions is even more problematic. But the presence of even a single modern carrier would have made things a LOT more difficult for the Japanese attacking formations.
As to a single carrier not providing enough air cover for the land battle, id agree with that, but then thats not the relevant question, either. It is whether the CAG could provide enough aircover for the two BBs, and whether the two BBs could then disrupt the seaborne operations that were integral to the japanese invasion. The British had certainly demonstrated in spades in the preceding two years that their CAGs were very efficient and could dispute enemy controlled airspace, even when heavily outnumbered