Research vs Internship Experience?

I'm a junior in computer science, and I've decided on pursuing a
MS/PhD program after I graduate. I need help deciding whether to get a
research position or an internship. Which experience will look better
on my resume for grad school admissions? I heard that it's easier to
get a good recommendation if you do research, and having a research
background looks good for grad school, but if I were to choose between
the internship and research, which would look better?