As far as ur format goes, lets see if I can help out.
Both Characters Air Game Against Each Other:
I would think Diddy has the better range, and Quicker aerials, making him to be better at this category. Just watch out for being above Pit, for an angled Pit U-air should knock you back out. For Pit, he can try to avoid your grand game a bit with a bit of air camping, but your aerials do have some good priority. I would think Pit's Air game is better than his Ground game with his multiple jumps, and such.
Both Characters Ground Game Against Each Other:
Diddy wins this with his annoying naners, and even with Pit's reflectors u can just trick the Pit into using it, and then go after him, or jump over him. Pit doesnt have as much range as Diddy, and the fear of the bananas make it harder for Pit to suppress him. Pit should try to stay in the air more to avoid naner locks more, however.
Moves To Avoid and HOW to avoid them:
-Arrows: The arrows themselves are a prime weapon that can be used to gimp you. How to do it, well, some suggested to recover low, to be out of Pit's shooting range. Be careful of a possible B-air that can knock you out of Up-B, or just Pit's edgehogging.
-Pit's reflectors: Pit's reflectors that can mess up your naner game. For this, this really Pits your mindgames against the Pit's mindgames (puns indended on Pit). So mindgames and prediction are the key here. Mirror Shield is easier to get through, just dont throw the naner at the Pit, and try grabbing him.
There has to be another move to be avoiding a lot, but I can't think if em atm. Use the 2 that I listed above in the meantime.
Diddy's Moves to Utilize In The Matchup:
Mastering the bananas are always a prime for Diddy. F-airs should be helpful when you get Pit off stage, and hopefully Pit is horizontal with u in the air to use the F-air. Although the Peanut gun isnt completely useful, you can use it for mindgames and possible gimping. Remember when charging the gun, u can cancel it with Shielding (On the ground only), and you could go off doing a fast glidetoss right there to improve your mindgames against Pit. Peanut gun can also try to knock Pit out of glide or ruin one of his jumps.
Personal Strategies To Help With Matchup:
Pit himself is one of the most versatile characters in the game. With 1 amazing projectile, 2 reflectors, decent speed, pretty nice recovery, medium weight, superb Ledgecamping tactics and edgeguarding, Pit can be played in many ways with different playstyles. Because each Pit would probably have a different style or way of battle, you should try to learn about the individual Pit you are playing, see what his/her tactics are like and try to surppress them.
Always try to master the naners, for it will limit Pit more. Whatever mindgames you have will help, and keep the Pressure up on a Pit.
The hardest Pits to deal with in the matchup would probably be a Ledgecamping Pit, or a Pit that loves to stay close to the ledge, since it keeps you from doing naner locks. If you mess up, you may get knocked off the stage, and go towards getting gimped possibly. I am good at ledgecamping myself, and can probably help with that strategy if you need it.
Overall Character Ratio:
As much as I want this to be 50-50 even, I say it is 55:45 your advantage. Without the naners, this could be 50:50 even, or ALMOST 55:45 Pit, but since any good Diddy will be on with the naners, it is ur slight advantage.
Stage CPs can be quite dependable for the Pit.
Hope this helps.
EDIT: Something tells me someone who I dislike may try to oppose me again (Not the Diddy players)
