I'm a long time SEO Content Machine user and I have tried WAC and Kontent Machine as well. Wac is good for fast and crappy content only. If you're really on tight budget you can go with WAC, but I strongly suggest you invest in content producing tool.
The real debate here should be SEO Content Machine vs Kontent Machine. While I do respect both and I think they are great, I think SEO Content Machine has a slight advantage. My overall experience is that SEO CM has better control over content and is more user friendly. Kontent Machine has it's own workflow which certainly is not bad, but it's kinda seems more linear to me. With SEO Content Machine I feel like I can produce anything and everything! Even if I need any kind of modification to the articles later, I can easily translate them, spin them etc... And most importantly I can insert custom content any way I want into already made articles. This latter one is huge if you are building quality tier1. But what I appreciate the most is the attitude of the developer of SEO Content Machine. I'm not sure if this guy sleeps at all. Just yesterday I've created 2 suggestions and reported 1 small bug into the vote system and he added both suggestions and fixed one bug in a matter of hours! This is really admirable! Really promising software with great future. When I buy software of 100+ I like to consider it as a long-term investment so I want to choose promising software with solid developer behind it.
So yeah, definitely SEO Content Machine wins my vote and I strongly recommend it!