Without abilities, Mega Pinsir is basically just a strong bug-type. It has no redeeming qualities and takes up a mega spot so it's not worth using.Dragon Tail...
Mew ofc is better and so are Rhydon and Dragonite but you might want to use Mew for something else and the others have 4* weaknesses
Weak to rocks ofc which hard punishes U-Turn and Drill can't really roost oof residual with its bulk
no 110% OP Status and lost points in SpD makes it alright at best, plus bug/fire/dark/poison moves are actually a (small) thing
The only thing good about them over others of the same type is taunt, Electrabuzz notably outspeeds Mew but both are fairly weak.
wtf pinsir-m is usable if not decent
maybe its me in candy mode again but its a beter SDer than Dodrio b/c bulk and power - nothing outspeeds Pinsir but not Dodrio