The main difference, to me, is that Doctorow has a less offensive way of making the case than RMS and hence might actually be taken seriously.
But now we see bills like SOPA and ProtectIP, and now we already have computers that you can't run any program you want on it, and all these other stories hinting that there are companies out there as sinister as RMS suggested. I find RMS less and less eccentric with each of these things that comes to light.
That said, RMS has been able to get attention. Whether we would be in a better place with an "normal" RMS is impossible to say. Maybe having both Doctorow and RMS is critical to the fight.