What looks better on your resume, the positions you have or the companies you worked for?

Long story short, I currently have a summer internship at a well respected company in their field, however neither the internship, company, nor the field that they are in are of any interest to me.

I just received a job offer at a relatively new startup (2009) that has little to no brand image or name, but is in the field that I want and the job would be doing what I have wanted.

Now my question is this, professionals of reddit, does it look better on my resume for an internship at a great company (in their field) or a full time job at a new company (that could end up being a bust).

Please note, I have no chance of getting a full time offer after the internship. I't is literally just a summer job.