I just spent two weeks learning Composite. It was ok for my 3d render passes cartoon compositing but it’s not stable. Crashes left right and centre, I think it’s free for a reason, sloppy program not meant for real world work IMO. Seems like an app made by non-compositors. Iff sequences are not the recommended format, tga or exr, no iff, iff is maya’s format and composite doesn’t like it as much as others, BS!
I just spent last week learning Nuke and it’s more then stable it’s teaching me what an image really is and how to manipulate it. It’s definitely a Pro app. I already feel comfortable with it’s advanced workflow. It’s an app designed by pro compositors tested in pro pipelines on pro projects and you feel that. If you like Maya you’ll like Nuke. Python is built right in like in maya and there’s loads of free tuts to get anyone up and running.
Fusion used it many years ago and I still call it Con-Fusion. Hard app to learn.
Go with Nuke because there’s loads of free tutorials and support and a future. Composites future is very unknown. Fusion would be second choice if you can figure it out and work around the 32 bit less support in areas. You use Maya so you’re probably use to Maya’s support in forums from being the most used, well nuke is the same but in the compositing field. Maya is king and so is nuke.