We all know Greninja is better suited to be a Special Attacker, but that DOES NOT mean physical Greninja is bad. It allows you to catch opponents off guard, Choice Banded Greninja (It actually can be pretty effective) can easily check both Mega Zards. More so, it's special movepool is actually WORSE then it's physical movepool, it just has the perfect coverage. Don't just say "Oh you can just switch into your physical wall after". Experienced players will know to U-Turn at the right time, switch into their special attacker, and there, they're forced to continually switch until both walls die.
Greninja is a late-game sweeper, it's physical side, with PuP allows it to actually be a decent sweeper. With a little bit of help, PuP a low health Pokemon and use your +1 boost to destroy souls. Greninja also only has 16 points less Attack than it's Special Attack, what ONE Pokemon actually cares about those sixteen points? The role physical Greninja plays is extremely similar to it's Special set, Physical Greninja just allows you to bypass some mons you normally wouldn't have fun against (Namely, Mega Zards importantly). Both have their ups and downs, but Physical is more or less outclassed by Special Greninja.
Greninja is a late-game sweeper, it's physical side, with PuP allows it to actually be a decent sweeper. With a little bit of help, PuP a low health Pokemon and use your +1 boost to destroy souls. Greninja also only has 16 points less Attack than it's Special Attack, what ONE Pokemon actually cares about those sixteen points? The role physical Greninja plays is extremely similar to it's Special set, Physical Greninja just allows you to bypass some mons you normally wouldn't have fun against (Namely, Mega Zards importantly). Both have their ups and downs, but Physical is more or less outclassed by Special Greninja.