What's remarkable is that once you've been compromised by the Genestealers, you're done for. There's nothing that can help you, you're a part of their hive mind, and you're essentially lost. By comparison, you can still convert most of the Chaos forces through radical recruitment if that's what you're into (yes, even with all the mutations), but nothing can save a brainwashed, generaped, despoiled individual. And it's ironic that the cult members operate under the belief that they will receive great reward and salvation once they bring their gods to the planet they infest, only to be betrayed and serve as nothing more than a midday snack for said gods.