Crobat
Pros
- Ridiculously fast
- Solid Attack
- Learns U-turn
- Aerial Ace is a decent move
- Can be good against Bruno, Erika, and to an extent, Giovanni
Cons
- Only decent defenses and HP
- Not too many options for physical attacks
- Friendship evolutions are a pain
Noctowl
Pros
- Great HP and Special Defense
- Decent Special Attack
- Can learn things like Extrasensory, Air Slash, Hypnosis, Reflect, and Shadow Ball
- Can be good against Bruno, Will, Erika, Koga, and to an extent, Giovanni
Cons
- Middling Speed
- Garbage Defense
It may seem like Noctowl is better, but I would choose Crobat. It's got a better typing, it's faster, and it can reliably deal with foes. Hope I helped!