I wouldn't take that wiki article as gospel. I noticed that it had RAF Phantoms replaced with Tornado F2, rather than the F3 and that the RN only got 24 F4K and the RAF 28, rather than the other way around. Nor would I take the brochure figures as a great indication of how the plane will perform in combat, after all not many dogfights occur between unarmed aircraft doing mach 2.1 at 60,000'. The Speys may lack in the top end but their performane envelope would be muh fatter, particularly when loaded with weapons and at lower altitudes where most combat takes place.
Just another word on the necessity of the Spey, the RN-FAA spec included the capacity to return to the deck with a full load of unexpended bombs on board. The USN dropped their unexpended bombs into the sea. So the RN really needed that extra low down thrust and bleed air for the BLC, way more than they needed those few extra feet of altitude or .2 of a mach.