It depends on what you want out of your physics degree.
"Internship" is a term usually applied to industry where people don't generally work in a physics capacity, they work in an engineering capacity. If you want to get a job in industry doing engineering or engineering-like stuff then an engineering internship would be a great idea.
If you want to do physics for a career (that is, be a professional physicist) then you are looking to go to graduate school for a PhD in physics. In this case you would usually be better served doing undergraduate research at your university (or a national lab if one is near you).