Is a content type or profile a better choice? I am working on a new site where I want to show information for art galleries, artists, museums, public art installations and art education. 

I understand both the content type and profile differences but can't decide which is better in the long run. I know the artists will need a profile and I would like to give the rest of the "types" the ability to edit their own content if they desire.

I have done a lot of research and can't seem to find an answer on how to link a content type entry with a user profile and am leaning toward profiles for everybody. However, this has drawbacks because of need for authentication info (which I don't know) as I create the profile.

Am I missing a magic module or some other clue?
You can use a profile, or a content type to expose information about a person. The difference between them is that a profile is always about an existing user account on the site.
For example, if your site is about emergent artists that will have a user account on your site, then a profile can be used from those artists to expose information about themselves. If your site is about famous past artists, then a content type can be used to expose information about them.

The other difference is that profiles are usually created from the users who want to add information to their own account. (The other alternative could be a user with the permission to administer users that adds a profile for another user.)
With nodes, out of the box, it's more difficult to limit who can create a node associated to the account of another user. 

As for linking content types to a user profile, it is possible to use the Views module to show a page that, for example, on user/%user/profile shows those specific nodes that contain information about a user.