TL;DR: absolutely yes it's competitive with CIDER; there may be experiments in the CIDER ecosystem that you won't get with Calva but 99% of the stuff you will actually use works totally fine in Calva and if you like VS Code you should definitely not think twice about it :)

Caveat: I don't use Calva myself, but I'm the president of the Clojurists Together Foundation. We just funded Calva's development and of course did some due diligence in the process. It's definitely got a ton of features, it's stable, but it's maybe slightly less feature-complete than the CIDER ecosystem right now. Hopefully funding helps change that, I'm a happy Emacs + CIDER user but rising tides lift all boats :-) One thing I love about Calva is that there's less fiddling. You just turn it on and you get 99% of the actual functionality of a top-end Emacs setup, except you didn't spend hours getting it to actually work. (Spacemacs makes this a lot better, but not everyone uses Spacemacs.)

While Calva isn't CIDER, it does build on stuff that is either directly from CIDER or de facto from CIDER (e.g. nrepl), so fortunately there's a lot of development effort that directly or indirectly helps both projects.

Finally, the shameless plug: if developing the Clojure ecosystem is important to you you should consider giving us (Clojurists Together Foundation) money -- we've funded critical infrastructure like CIDER, fireplace, Ring, Reagent, shadow-cljs... Oh, and we keep a little thing called Clojars afloat :-)

It will depend on what features your workflow appreciates. Being the creator of Calva I am biased, of course, but it certainly supports my workflow.

The big culprit right now is that Calva doesn't handle large results well at all. I find strategies around it, but it is a thing that really needs to be fixed and it will be in focus during the Clojurists Together funding.

Another feature lacking, that CIDER has, is a step debugger. Something that doesn't affect my workflow very much, but I know some people will lack it. It is also part of what we will try to fix during the CT funding period.