You could argue the shadowcaster is better than a pwt. If you play well with the mobile arc your 2 blind spots don't matter. Plus you negate auto thrusters at range 1-2.

It has been argued but that doesn't necessarily make it true.

If you "play well" then only being able to fire out of your primary arc is all you need. Of course that depends on how you define "play well" which some seem to think that running a PWT no longer requires. Your blind spots may not matter until you run into someone who plays better than you and any actions taken to move the MFA are actions that likely could have been spent elsewhere.

Getting to negate Autothrusters at R1-2 if you happen to have your MFA pointed the right way is great but it isn't everything. If it actually becomes a big selling point and Autothrusters suddenly become useless because of the MFA it will stop being used at which time your PWT probably becomes a better solution.