I use SnappyApp, which adds annotation and sharing features.
Also ‘floats’ the screengrab over everything else until I dismiss it, which might not sound like something that is very useful - but wow, something I use all the time, every day just about.
It also allows you to search through the library of past ‘snaps’, which might (or might not be) something to consider…
That said, there is nothing wrong with the built-in features – I just wanted a bit more.
Before using a specific App, I had Hazel watch the folder the default screengrabs would be saved to (think this can be set as well, if memory serves), and have them tagged/moved/renamed to something I found useful at the time. Not necessary, but something to consider if you happen to use Hazel.