Well, we're assuming the wolf player knows how to deal with bananas too. I mean, bananas are still the biggest problem in this matchup, but if you're as good as the diddy they shouldn't completely screw you. As long as you know the matchup fairly well and have banana experience, you have a slight advantage. Compared to many other characters, wolf can counter diddy's bananas pretty well.
Of course, a good Wolf player will know HOW to deal with bananas, it's just a matter of execution, whether or not the Wolf actually DOES deal with the bananas.
On the subject of how well Wolf deals with bananas... yes, Wolf has more options than most characters, HOWEVER, I'd like to say it's not as simple as "Reflector when diddy throws a banana" or "SH Fair when he's about to glidetoss" Unless you have super-human reaction time (Lol computers) then that strategy isn't going to work, you're going to have to use your options based on when you PREDICT Diddy will throw his bananas, and if you start catching a banana or two, he has nearly the same options to get it back (SH Airdodge, dash attack) And if you start catching them, he's not just going to keep on throwing it where you can catch it, he's going to mix up is timing to throw you off. Let me give an example, Wolf vs GaW, game and watch has a deadly counter to Wolf's blaster, the bucket. However, Wolf players STILL use lasers against him, and aren't punished nearly as much as THEY SHOULD.
If it were that easy to predict it, then Wolf wouldn't use lasers against GaW.
Just an example, but you guys should get my point. The Wolf STILL has those options PRESENT, and he still has the KNOWLEDGE of HOW to counter the bananas, however, simple timing can PUNISH those attempts at predicting the bananas, since you don't know exactly when a Diddy will throw his bananas.
All that being said, I think it's fairly obvious that this entire matchup revolves around countering Diddy's bananas,, because that's really his only reliable approach. Unfortunately, the banans aren't easy to counter.
WITHOUT the bananas, I feel this would be in Wolf's favor, Wolf's aerial game and ground game simply beat out Diddy's (Bananas aside). If Diddy is below the stage, his recovery is stupidly predictable, you can usually get a well timed Dsmash off in order to kill in that situation, however, that's only if the Diddy manages to get below the stage (A good way to do this imo is to hit him with a laser, takes away his jump =D ) However, Diddy still has an excellent off stage game as well....
So all in all, I call the match-up even. Without the bananas, Wolf easily has the advantage 60:40. I'd say easily has 65:35 but Diddy has an off-stage game that's decent. So eh, if you're facing a Diddy where you can counter the bananas, great for you, you now have the advantage. However, if you're playing a smart Diddy, that won't predictable throw his bananas and will mix up his timings, then it's even.