Only advantage a Katana has at the moment is Movement speed.
Also weight and the ability to decap stuff with 1 hit instead of ~2, not being hugged by headless enemies and consequently being able to actually run through enemies.
If you have a saw, a clot actually is an obstacle. A ~.5 cecond obstacle but still an obstacle.
You can't march through an ocean of clots.
All chainsaw berserkers I have seen so far were nothing but damage sponges, more of a liability than actually useful.
You are a lot more prone to taking damage while carrying it and there aren't really enough advantages that you won't get from the katana.
I wish they'd fix the chainsaw so it's the thing we know from the beta: An actually viable alternative to the katana.
Just give it barely enough damage to decap trash with 1 primary hit and that's it. That's the barrier between "meh" and "awesome" imo.