Kontent Machine 3. One off fee, and updated so often
KM 3 has a specific adult filter on/off. If you turn it on. Expect a deluge of adult. If you turn it off... zero.
Just yesterday they added cloud functionality. Your campaigns available from anywhere via an API call. The hosting is (of course) free to all users, subs or one off fee.
Not a fan of WAC. It's quick to get a campaign going, but has fewer sources, and the content - while many claim it's more readable, is readable because it's not properly spun (and therefore duplicate).
Once you spin it, then KM has the edge as it seems to find far more sources and you can have a lot greater control over the output.
But it's a tool. Set it up to produce crap - and it will produce crap. That is the same for both products.
Scritty