Though they have the same types, they have very diffrent roles,
Honchkrow is more focused on Sweeping and offensive
While mandibuzz is more focused on Stall. (Since it can learn Toxic and roost)
Taunt is also a great add for it considering its average speed to stop slow set uppers
Honestly, i would say i prefer Mandibuzz because Dark and Flying is more focused on defence than offensive in my opinion.
Earth and Psychic immunity can be a great add in your team, Especially works really great with Poison partners.