Whirl, I'd happily take you up on your offer to kill someone in their ride of choice. First we can both fly 109s (any varient you'd like)- then we'll both fly the P-38.
EDIT: After we are done doing that, we can also go 109 vs P38- you can tell me which 109 to fly.
I happen to be of the camp that thinks the 109 is a lot tougher to master than the P-38. I am also of the camp that believes the 109 is a much deadlier plane than the P-38 once you've mastered it.
In my opinion, the P-38 is a great plane for middle of the road pilots. It is slightly to difficult for newbies (at least newbies that like to turn, a natural E fighting newbie like I was could have some success in it), but it doesn't offer as many advantages as some planes do to the advanced, possibly sneaky (lol) pilot. Citabria is an exception to this, but he is great in any plane.
Actually.. that came out a bit stupid. This sounds even dumber as I write it, but I'll try to explain it and maybe someone will make sense of it. Everyone knows what the P38 can do- or at least they think they do. For instance, I KNOW the P38 will outturn me if I am in a 109-G10. Hell, a P38 will outturn just about any 109 at the same speed. People get used to seeing the P38 fight a certain way- and that is usually the best way to fight in it. The P38 is a great TnB plane if it starts off with an advantage (like altitude or position). The P38 has really bad high speed handling, everyone knows that.
Now, as far as advantages the 109 (for instance) offers. Everyone knows pretty much how the 109-G10 performs. Some people underestimate it, which is good for the G10 pilot. People get used to seeing the G10 BnZ- but in my opinion that is NOT the best way to fight in it. The G10 is a very capable turnfighter, provided your opponent is not a Spit, Zeke, or Niki. Or a good pilot in an La7 or a Yak or a P38 ( bad pilots are fair game though

). Most everything else the G10 can turn with.
What makes it even better is there are multiple versions of the 109. The G2 turns better than the G10 and has more speed than the G6, but you sacrifice some firepower by losing the 13mm MGs. However, for the aggressive 109 pilot this matters not. People in La7s and such will see you 'try' to turn your 109 and get sucked into a turnfight that they will lose. The F4 turns even better than the G2 plus it has a German camo scheme so it isnt as immediately obvious that you aren't fighting a G10. The E4 can turn with a poor pilot in a Spitfire or Niki (good pilots in either will shred a 109E though).
That is what makes the 109 more fun in my opinion, but also more challenging. You need to know the strengths of your plane, and you need to know the strengths and weaknesses of the enemies plane. The P38 is in the same boat here, but I really think it is a more competetive plane overall than any 109 except the G10. Anyway, my long, incredibly convoluted, and nonsensical post is over. I'm tired, lol.