Shadow Persian

Sorry all, the fact that Shadow Persian is basically Giovanni's pet (that he literally abandons as soon as it loses) doesn't make it much better than the base version. 

Best PvE Offensive Moveset

• Feint Attack and Foul Play are great Dark Type moves, but don't benefit from STAB.
• Scratch is not good.
• Payback is a downgrade. 
• Night Slash is not worth the Elite TM. 
• Play Rough and Power Gem are basically useless for Persian.

Best PvE Defensive Moveset

• Feint Attack has solid neutral coverage... unless you're defending against a Fighting Type, which you probably are.
• Feint Attack has okay-ish neutral coverage... unless you're defending against a Ghost, Steel, or Rock Type, which you probably are.
• Night Slash* has the lowest energy cost, making it ideal for defense. Just please don't waste an Elite TM getting it.
• Play Rough is generally the move of choice on defense, as it has great neutral coverage and high power.
• Power Gem is the same story, but a bit weaker.
• Foul Play has the issue as being the same type as Persian's best defensive fast move, making it less attractive in general.
• Payback is undesirable for defense as a 1-bar move. 

Feint Attack, while it lacks STAB, has better energy generation than Scratch.

Night Slash requires an Elite TM, but its low energy cost allows it to pressure shields easily. Foul Play deals more damage but its higher energy cost makes it less desirable. Do note that pairing both Dark-type moves together is not advised due to the lack of coverage. Power Gem provides wide coverage with its Rock typing, but its damage output isn't very impressive for its moderately high energy cost. Play Rough can be useful for its Fairy-type coverage against Fighting-type opponents, while Return benefits from STAB to deal the most neutral damage, but both moves cost lots of energy to use.