Lets pretend we are fighting an exactly equal conflict.
Equal in all respects. Pilot skill, tactics, aircraft ability, battlefield, radar etc.
Then the 109 will always win. Because in this sort of war we are talking a war of attrition and the deciding factor will be the time to build the aircraft.
The 109 was easier and quicker to build than the Spitfire.
But … Spitfire production outstripped Bf109 production during the battle (IIRC), although neither side came particularly close to running out of aircraft …