What are the relative strengths and weaknesses of the following three environments? 1. REPL in terminal. 2. Emacs + julia-mode + julia-repl-mode. 3. VSCode with Julia extension.
Specifically, between the Julia plugins for Emacs and VSCode, which one is more actively maintained? Which one has more up-to-date syntax highlighting given that Julia has an evolving syntax (e.g. new features in v1.7)? Is Revise.jl support still missing from VSCode?
Using a repl in the terminal is in a different category than the two IDE options you mentioned. You can use terminal for quick interactive jobs, but I wouldn’t use it for writing programs.
For IDEs, VSCode vs Emacs is a much bigger conversation and there is no simple answer. VSCode has more users. Emacs has a lot of power unavailable in any other system.
We expose the standard REPL in VS Code with lots of extra integration, so you can use that as well from there.
I’m pretty sure we are all using the same syntax highlighting rules.
Revise.jl has been supported in VS Code for years 
We even have an option to turn it on and off.
When it comes to things like this, you really just need to explore for yourself and see what works for you. I use VS Code, but I used to use vim.