I am a big fan of cygwin and have been using it for years. If you’ve installed it and choosen the default install you’ll at some point run into a missing command and will have to run the setup program again. After a few iterations of this you’ll wonder about installing the whole thing. If you have the space it certainly makes your life easier in the long run.
A couple points to consider.
I just did a full install on a machine and it looks like cygwin has taken 3.21 gig of space.
Also, when you do install you should pick a time to just let it run. Also, it may take a few retries as you may have a “download incomplete” message after a time.