Undergraduate research

Hi, a month ago it was brought to my attention that I will need some sort of research experience as an undergraduate if I want to be considered by a "top" university's graduate program ("top" university - MIT, stanford, caltech, etc). I may have an opportunity to do some research in computer science dealing with artificial intelligence/machine learning. Also, I have an opportunity to get an intership at an engineering firm dealing with something about radiation effects on electronics. Will the computer science research look particularly good on my application, or will they really care? What about the engineering internship? (I'm not really sure I"m qualified for it since I haven't taken much modern physics but oh well). I need to decide quickly, but I don't want to rush headlong into something that isn't going to help me out so I'm asking a few sources for advice.

This might seem like a poor way to decide which universities to shoot for (which ones are considered the "best"). Perhaps I should find some subfield I"m interested in pursueing and then figure out which universities are involved in those fields, but the "top" universities do seem to have a lot more options as to what fields you can specialize in. Having not really taken much modern physics yet, I'm uniformed so I can't really know what the heck I"ll want to specialize in at this point.

I should mention that I'm going into my 5th year at a state university, where I'm majoring in Computer Science and Physics (seperatly; 2 degrees). Should have 1 or maybe 1.5 years left. Have not taken the GRE yet, because I haven't taken quantum mechanics or optics, which are on the physics GRE. GPA is 3.9.