This may be the blind leading the blind, since I'm just an MS-4, but I do not think my application was harmed much by the fact that I had no neurology Sub-I or away rotation.
There is no neurology department at my school, and I chose neurology late in my third year, after away rotations had already been scheduled. I did a month of neurology early in my 4th year with a private attending. I got interviews nearly everywhere I applied; although I did not apply to "elite" top 10 programs, I got plenty of interviews and I do not anticipate having any trouble matching (now watch me jinx myself with this post!).
So, in my experience, it doesn't make a whole lot of difference whether you do a Sub-I or an away rotation, as long as you can explain your decisions on the interview trail. This is not a hyper-competitive field, on the whole.