I think the pre-installed ones are garbage compared to dedicated ones, depending on what you are buying for a dedicated external one. I mean, a $10-$20 webcam will probably be the same/similar as your built in one. Something like $50-$100 would be MUCH better, and of course up from there.
I would say do some recordings, maybe post in the review area to ask people what they think of its quality, go from there.
This is $500! I don't make that much from my Youtube channel to invest like that in it. I do have a lighting umbrella and good lights for inside. I just want something easy to use to quickly film my vlogs when I have emotional thoughts I want to share. I use a handheld digital camera to film outside videos.Your better off buying a video camera like A Sony HDR 220
Better quality video, e.t.c, and if your doing blogs get a lighting umbrella also..