To me, they're two different styles in many ways. I see EVH as more of a rock guitarist, and Randy as more of a metal guitarist. Randy certainly did more to expand and further metal guitar. EVH did lots to further rock guitar.
While some may argue that rock and metal guitar are the same, I beg to differ. I also think that EVH was more extroverted than Randy, and tooted his own horn more. Randy was considerably quieter and more modest.
In some ways, they are yin and yang.
The big difference is that Ed has lived long enough to see his playing become passé and outdated. Most every new rock player has Van Halen-esque chops to play at an international level. Metal guitarists more so.
Ed has not done anything groundbreaking for years. He noodles away on old tunes and is stuck in a rut. Randy passed away before he saw his style become passé.
Now I might be a bit biased, but this is where Randy had the edge on Ed. Whereas Ed was, and still is, stuck in a certain style (albeit one that was important for its time), Randy's extensive knowledge of music in general, and appreciation of other forms of music, would have carried him further in his musical journey. I think there is little doubt he would have transcended genres. Sadly, we (and he) didn't get the chance to see this happen.
EVH and Randy were/are monster talents, but only one, Randy, was a true musical prodigy. EVH was not. He was/is an exceptional player that made his mark on music at a certain point in time, and has lived on that ever since. Randy's work shows progression, even over the course of two albums. Can we say the same of EVH? IMO, no.
