OK I will give an Overview of each to help you decide :)
Pidgeot
Pidgeot's best 3 stats are Speed (91), HP (83), and Attack (80). As you can tell by that he is not particularly strong and his move pool is the typical bad bird Pokemon Move-pool. Nothing that really stands out about it. The best set may actually be a Choice-specs set and use Air-slash, Heat-wave, HP(Ground), and Uproar/Ominous-Wind.
Skarmory
Best 3 stats are Defense (140), Attack (80), and Speed and Special Defense(70). He is an OU defensive Pokemon and has lots of talent in the use entry hazards. He has a decent move-pool that supports him Attacking and Defending. A good moveset would be Roost, Stealth-rock, Whirl-wind, Spikes/Brave-bird.
Aerodactyl
Best 3 stats are Speed (130), Attack (105), and Hp (80). A great UU Physical Sweeper who can also abuse entry hazards. He has a colorful move-pool that is great for his physical sweeping and annoying. There are a lot of moveset options for him but I prefer straight forward sweeper: Rock-slide/Stone edge, Earthquake, Crunch, Iron-head/Elemental fangs.
Honchkrow
Best 3 stats are Attack (125), S.attack (105), and HP (100). A great revenge killer but he sadly lacks defensive bulk with his 52 defenses and he isn't very fast at only 71 so basically he relies on Sucker-punch to destroy his opponents. He has a decent move-pool on both physical and special sides with both supportive and offensive options. A good moveset would be: Brave-bird, Sucker-punch, Steel-wing/Super-power, and Thunder-wave/Roost.
Staraptor
Best 3 stats are Attack (120), Speed (100), and HP (85). He is a straight forward suicide sweeper with great attack and decent speed he hits hard then goes down. He has the typical bad bird Pokemon movepool accept he has Close-combat which gives him a good coverage move against Ice and rock types and even Steel types unlike the rest which rely on Steel wing for Rock and Ice coverage. A good moveset would be: Close-combat, Return, Brave-bird, and U-turn.
So Pidgeot is definitely the worst of these only use it if it is your favorite Pokemon or something. As for the others use Skarmory if you want an entry hazard Tank, Areodactyle or Staraptor if you want a Physical sweeper. Or Honchekrow if you want a revenge killer.