The two @RoyalNavy fighter squadrons that are recorded as having participated in the #BattleOfBritain were each equipped, or equipping with the best naval fighters then available.
808 Naval Air Squadron formed on 1st July 1940 flying the brand-new, two-seat, Fairey Fulmar #WW2 https://twitter.com/ArmouredCarrier/status/1296971973524729857

804 Naval Air Squadron, on the other hand, initially flying Gloster Sea Gladiator biplanes, began re-equipping with the brand-new, single-seat, Grumman Martlet, the first of which arrived from the US on 27th July 1940 (reaching 804 after some upgrading/alteration by Blackburn)

Here (in a slightly mistitled @BritishPathe newsreel) a group of @RoyalNavy Martlet pilots are apparently familiarising, & testing against a Hurricane, the performance of which the Martlet broadly matched (albeit with noticeably superior range & firepower)

If one were inclined to stir, one could make a cheeky case that competitive speed/manoeuvrability, plus superior range & firepower gives the @RoyalNavy a claim to have had the best fighter in the #BattleOfBritain, but in truth the early Martlets lacked the necessary armour &...

self-sealing fuel tanks that had been shown to be necessary, while the mountings for the big, US 50cal guns that gave that added firepower were troublesome, leading to frequent jams. Also, 804 only declared themselves ready on the type at the end of September - very near the end.

One other issue with the early Martlets was a lack of folding wings, vital for work aboard aircraft carriers. This, & other issues would be rectified with the next batch, but the work required a six month delay, so they would not arrive until March 1941

The requirements of the @USNavy (which also urgently needed large numbers of these new aircraft, which they called the Wildcat, to replace their own biplane Grumman F3F fighters) left the @RoyalNavy needing to supplement numbers with Hurricanes & Spitfires adapted for carrier use

Nonetheless, when they started arriving in 1941 the folding-wing Martlets gave the @RoyalNavy a potent, single-seat, monoplane, dedicated naval fighter, which served well aboard big fleet carriers, & small escort carriers until supplanted by the new generation Hellcats & Corsairs