Okay, so:

All long-range AA suck without radar.
Two Threshers will deal more damage to 10 Ravens provided the ravens are clumped than a single Chainsaw. They also do more damage to Likho too.

However all AA seems to suck at killing planes before they drop their payload - but succeed at killing them afterwards thanks to their damage. I think this is a design decision to force players to make tradeoffs of killing a target vs losing planes.

If you want something that kills planes then Hacksaw is the best. Making just two or three can stop just enough Ravens that your comm or factory or whatever survives a raven suicide attack.