Li all depends on the frequency and the type of coax, that you can tell a noticeable difference. As BushDoctor pointed out, a lab session, you will notice differences but the human ear won;t notice much. Now if you want to use uhf frequencies, well the best coax and the sorter difference is important. Now if you are doing low band, on 80 or 40 meters, long runs don't make much of a difference.