Each mark of the Spitfire and 109 seemed to attempt leap-frog over the other in a continual tug-of-war in terms of performance, but they are generally remarkably even.
The matchups are quite interesting, and show the continual push for more speed and climb throughout the war:
1940: 109 E3/E4/E7 vs Spitfire I/II
1941: 109 F1/F2 vs Spitfire Vb
1941/1942: 109 F4 vs Spitfire Vc
1942/1943 109 G2 vs Spitfire F. IX
1943-1945: 109 G6/G14 vs Spitfire LF. IX/HF. IX, Spitfire VIII, Spitfire VII
1944/1945: 109 G10/K4 vs Spitfire XIV
Plus some oddities like the low altitude Mk XII, high altitude Mk VI and the very late Mk XXI (even if it only flew 154 combat sorties in the war
)
I'd say that the continuing strength of the Spitfire lay in the adaptability of the Merlin for various roles, particularly with the 2 stage Merlin 60 serise (61, 63, 63A, 64, 66, 70 and 71) and the low altitude Merlin 50 serise (50, 50M, 55M) which kept the Mk V in frontline service up to mid 1944 as a low-alt fighter bomber
Schwartz:
I'm simplyfing a bit, as the performance of the early 109s and Spitfires chopped and changed a lot. Here's what i have to go on, after spectating at a REALLY detailed thread (like calling the engine manufacturers and spending $600 on BMW technical manual detailed) at the Aces High web-board about 2 years ago:
The early 109s weren't quite as fast as the early Spitfires. The kenblatt for the Bf 109E1/E3 with the DB 601A at 1.23 ATA/ 2,400 rpm gives a figure of 555 kph/344 mph at 4.2 km/13,800 feet. A contemporary 1939 Spitfire I was doing 590kph/366 mph fully loaded, but unlike the 109, it wasn't a battle worth machine at the time.
However, the DB 601A-1a fitted to the 109E4 and some 109E3s was uprated to 1.30 ATA for 5 minutes combat power. It gave the 109 an extra 15 kph/10 mph at all heights below about 7,000m. So a Battle of Britain 109E4 was doing about 570 kph/354mph at 4.5 km/ 14,500 feet. A contemporary 1940 Spitfire was doing 351-354 mph / 565-570 kph, losing 10 mph or so because of all the extra equipment and the new prop. However, it was doing that at about 18-20,000 feet.
Finally, the 109E4/N and E7 recieved the DB 601N, which ran at a higher 30 minutes rating of 1.25 ATA, but was never cleared for a 5 minute 1.3 ATA combat rating (which doesn't mean that the engine wasn't run at 1.3 ATA, it just wasn't officially done
) The 601N had a higher full throttle height than the 601A/ 601A-1a. Speed rose to 575 kph/ 357 mph at 5.1 kilometers/ 16,800 feet. It was also better below full throttle height, being some 10 kph/6 mph faster than the 5 minute rating for the DB 601A-1a up to full throttle height and some 25 kph/ 16 mph faster than the DB 601A at all heights.
So basic story is:
109 E1/E3 DB 601A:
460 kph / 285 mph @ sea level
555 kph / 345 mph @ 4.2 km/ 13,800 feet
109 E3/E4 DB 601A-1a:
480 kph / 300 mph @ sea level
570 kph / 354 mph @ 4.5 km/ 14,500 feet
109 E4N/E7 DB 601N:
490 kph/ 305 mph @ sea level
575 kph/ 357 mph @ 5.2 km/ 16,800 feet
Early Spitfire I Merlin II/III:
455 kph/ 282 mph @ sea level
590 kph/ 367 mpg @ 6.1 km/ 20,000 feet
Spitfire I Merlin II/III with 100 octane and +12.5 lbs boost:
500 kph/ 310 mph @ sea level
570 kph/ 355 mph @ 6.1 km/ 20,000 feet
Spitfire II Merlin XII:
515 kph/ 320 mph @ sea level
565 kph/ 351 mph @ 5.5 km/ 18,000 feet.
The Spitfires would of cruised at lower speeds below about 13-14,,000 feet than the 109s, but faster than the 109s above about 17-18,000 feet.