Yes that's pretty much it in a nut shell.
Last time I used the built in one in the HTML Editor (quite some versions ago so this may have changed since then), it did not allow it to be minimized at all so you had to use it and then it would close. That's the main reason I use the stand alone version, so it can remain open at all times on my task bar as needed rather than one use at a time.
The other thing I'm not sure of is if the built in version has all the features of the color schemes so you can save them. I believe it does, but I'm not sure.
I would highly suggest taking both of them for a spin (if you aren't using the HTML Editor already that is) and see first hand what if any differences there are so you know. This gives you a much better way of being sure you are getting exactly what you want, no guess work needed.