Thought maybe the nosecannon 20mm was a heavier shell, or an 'exploding' one.
Hmz, so the cannons are equal,but the spit has 2 and fire faster

So ehm, maybe a stuppid question, but where does the 109 exel the spit in? (dont say speed because thats a tiny difference)
EDIT:
I just found this table
http://www.geocities.com/CapeCanaver...n/fgun-ta.html
More or less half way, there is the spit mk IX with the 4 x 7.7mm and 2x 20mm and exactly under the IX, there is the G-6. This G-6 is armed with a 20mm cannon and 2x 13mm.
So those 2 are have the same armament as the IX in game, and, lets say the 109 F-4 (the G-6 in game has gunpods).
If you look at the table, the weight of fire of the 109 is HIGHER. It is 2.46 kg per second, and the spit has 2.24 kg per second.
Looking at this, I would asume that the 109's armament should kill quicker than the spit's.
Do I just have a lot of bad luck with the 109/ luck with the spit? or is the armament of the 109 much weaker than the spits