An Unfezant with a neutral nature and 252 EVs on Special Attack at Level 100 will have a Special Attack stat of 229. Wit a positive nature, that becomes 251.
Without any EVs onto Unfezant's attack stat, Unfezant's attack is 266. This is higher than Unfezant's maxed out Special Attack
The only case where Unfezant's attack would be lower would be if it had a Nature which decreased Attack or it lacked IVs on its Attack
In contrast, an Unfezant with a positive nature and 252 EVS on Attack at Level 100 will have a very respectable attack stat of 361.
Physical Unfezant will basically always be stronger than Special