1h Chainsword has an elongated delay after a push (not the push attack stab, just the push) before you’re allowed to do a light or heavy attack. This means if you want to avoid using the (frankly useless) stab attack, you’re putting yourself at a severe disadvantage while your character kind of just holds the chainsword in front of them doing nothing for an annoyingly long period of time.
For reference, here’s what the delay is like. The push-push attack-light combo is rapid, but going into a light after a push has you do nothing for an infuriating amount of time.
And here’s the Catachan Mk VII Sword for comparison - much more snappy on the push into light. For reference too, the push into heavy takes about the same amount of time as the chainsword.
The 1h Chainsword in general needs more love.