Generally, Chaotica serves as a far better rendering platform, and is substantially faster than Apophysis. It doesn't support all 3D camera effects that some people add in Apophysis, and also costs money if you're looking to render larger images out, but the cost is easily worth the time saved imo.
In terms of learning the software itself, both pieces of software are a bit quirky, but have a lot of overlap between using them. It's probably easier to start out with Apophysis because the editor is much more polished. As for tutorials explaining how to use this, I have [BasicsTutorialPreview
] and [Tutorialthing
], which is woefully unfinished, but an attempt and describing how the interface works and how I interact with it. If you have any more specific questions, that might make it easier for me to explain things I normally would take for granted just from using these programs for so long. There's also a discord server I'm on which contains some remnants of the old chatroom, which is where I initially joined up and learned a lot from people there, and I'd be happy to drop you a link if you're interested.