VS for Mac is a full-on IDE, is significantly larger, and comes with lots of stuff to build a variety of apps.

VSCode is a text editor that, combined with the Ionide plugins, gives you a great lightweight IDE-like experience. It requires a bit more setup, but it's great if you prefer a more lightweight experience but still want a bunch of great features.

I use both depending on what I'm doing or what I feel like using. Typically I'll use VSCode for smaller projects or one-off F# scripts, but you can use it for just about anything. Ionide itself is actually built using Ionide, so that's a great example of using it for something bigger.

I can't speak to Visual Studio for Mac, but the Ionide plugin for VSCode is very impressive. VSCode will fire up faster than Visual Studio for windows and use less resources, ionide has some features Visual Studio does not. There are pros and cons, some people hate Visual Studio, some people prefer it. I prefer Visual Studio but Ionide is not bad when I'm in Linux.