PSW on an MVAM isn't nearly as effective as it is on a BOP, because your opponent has more time to prep for the stuns.
Not really. Maybe if that MVAM is doing hit and run like a ******, but if he (or any other ship) is engaged in the battle the entire time good luck calling when he's going to use the PSW. And even if you are able to guess correctly when you need to pop A2damp an enemy pilot with an ounce of skill will just wait for it to wear off to psw/spike you.
With BoPs that do hit and run at least there are ways to realize that they are coming in for an attack (sounds, detection...) which gives you an indication of when to counter.