Mandibuzz

Mandibuzz is more hyped for PvP than for PvE. A poor ATK stat for gyms and raids leaves little use in PvE for this bird. Its respectable DEF and STA stats make it a decent defender for gyms, though Air Slash is probably recommended for that role due to common Fighting-type attackers. Better to use Mandibuzz for PvP, where it really shines. 

Best PvE Offensive Moveset

• Snarl performs the best, and should be paired with Dark-type charge moves for that role.
• Air Slash should pair with Aerial Ace for the Flying-type role. 
• Foul Play performs better than Dark Pulse due to its much shorter cooldown animation.
• Shadow Ball is very strong even without STAB, but is slightly behind Foul Play. 

Best PvE Defensive Moveset

• Air Slash deals slightly more damage on defense.
• Snarl generates slightly more energy on defense. 
• Aerial Ace can be spammed frequently, being a 3-bar move, but doesn't hit very hard.
• Dark Pulse is slightly better on defense than Foul Play due to its higher base power and earlier damage window.
• Shadow Ball hits hard for neutral damage, but is the slowest and easiest to dodge. 

Snarl is preferred for its high energy generation, letting Mandibuzz access its charge moves sooner. Air Slash sports greater damage output and offers Flying-type coverage, but falls behind in energy gains.

Aerial Ace isn't particularly a strong move, but offers STAB Flying-type coverage and is its cheapest Charged Attack. Dark Pulse and Foul Play are both good Dark STAB options, but Dark Pulse is often preferred due to its higher DPE, and Aerial Ace already covers Mandibuzz's need for a low cost move. Shadow Ball lacks STAB with Mandibuzz.