Masquerain

Masquerain is a beautiful Pokemon that won't be taking down any raid bosses anytime soon. Bug and Flying-type is weak to Rock, Ice, Flying, Electric, and Fire-type. This mon doesn't have any statistical advantage over the rest of the Bug-types or any redeeming movesets either.

Best PvE Offensive Moveset

• Air Slash is clearly superior to Infestation for DPS, but the latter sports the same type as Masquerain's "best" Charged Moves
• Silver Wind has STAB and is a 3-bar charged move, giving it the most potential to get hits in. 
• Lunge is a weaker Bug move.
• Air Cutter, Bubble Beam, and Ominous Wind aren't relevant on offense. 

Best PvE Defensive Moveset

• Air Slash outperforms Infestation for damage on defense. 
• Silver Wind has the most damage potential, followed by Ominous Wind. 
• Lunge is an inferior choice
• Bubble Beam is weak, but its typing could be at least a bit useful.
• Air Cutter isn't relevant on defense. 

Air Slash provides stronger damage output, given that Masquerain has poor charge moves. Infestation generates energy more quickly, but Masquerain's charge moves are quite bad.

Lunge is the main charge move of choice, dealing decent STAB damage while ensuring a guaranteed ATK debuff on the opponent. Bubble Beam can debuff the opponent's ATK for 5 less energy, but its damage is pathetic. Silver Wind is redundant due to its worse damage output, and the small 10% chance to proc is self-buff is unreliable. Air Cutter is a very poor move that demands a moderate amount of energy to use, but at least it gets STAB.