Event Image vs Source
Genosis
Theres always a number of ways to do things, sometimes one way is better than another if you have other plans later on for adjusting the templates, but if they both come out the same now and you have no plans to extend currently, then I think its an either/or situation where either works.
An example:
You can add an image as a blog post image or you can add an image TO a blog post. Both end up showing the image on a blog. The advantage of the first is that you can check when searching to see that the image exist before showing the post in a list, the advantage of the second is more flexibility in where in the post the image comes out, but the first way you can make a more uniform structure......... but.... and.... but.... and.....
whichever is ok.