I don't manually spin, and Spin Rewriter produces reasonably good automated content with strict settings. The daily API allowance is pretty generous (300 calls a day IIRC) as well. You do trade a lot of uniqueness for more readability, but I've found that (for my purposes at least) I can get around this by mashing together content from different sources, so like a 500 word article with 5 100 word paragraphs from different places.
I've used the other 3 that you mentioned too. Article Builder content is way overused, to the point where you would be just as well off using lightly spun article directory content. Probably because it got so popular with GSA SER users 3-4 years ago. Article Forge is interesting but I wasn't satisfied with the readability of the content no matter what I did. WordAI does a good job, perhaps even better than Spin Rewriter, but it's overpriced and I found it hard to use, especially to bulk spin a ton of articles.