I've got just 2 now. Codium and Blackbox.ai. Not because they're the best, but because I'm a cheapskate hobbyist and they're free :)

I'm only just starting to play with AI tooling, so I don't have an opinion on which is better, but something about the way Blackbox worked within VSCode means I went through the hassle of getting it installed to vscodium when I switched.

I suspect that Codium might be better at oddball stuff, though, like OpenSCAD. Blackbox seems to just make bad guesses while trying to regurgitate code I've already written. Codium seems to have at least a primitive idea of what's going on with OpenSCAD. But Blackbox does a great job of cleaning up my comments and even generating decent comments for uncommented code.

FWIW, Codium actually labels OpenSCAD as "experimental", but I don't know if that's just boilerplate for something it's never been trained on or whether there is some training data in its system.

Blackbox is a pain to work with in other ways, though. It was like pulling teeth to get an account and I still can't find anything on their pricing--or any documentation, for that matter--despite language suggesting that there are different tiers and a chat UI that offers different settings (like web browsing mode and fun mode). And the Blackbox name isn't doing it any favours, given that "black box" is a generic term in the AI community and others. It's own chat doesn't seem to know that a question about the service might be about the service instead of the generic term.