I've used wordai, KM3, wordai+ chimp rewriter, and I own WAC with the tier1 upgrade.
I'll say this.. WAC requires more work/effort than KM3.. But it also gives you more control over the output if you really know what you are doing when scraping with scrape box, plus the any site scraper in the premium version is awesome. I prefer WAC with the premium upgrade over KM3, even though it does take more time/skill.
Sometimes, if I am really bored I will download articles from wac that I scrape with scrapebox (from wherever not just article directories) then rewritethem using chimp rewriter and wordai, then import them into WAC of the build and export into GSA, and that works good too. but I have spent some time learning how to use WAC and it works great for me. I like it.