It's just not a black or white situation. Although, it does also beg the question of how will people get there to walk/bike on this trail?
In Sonoma and Marin, there's a lot more opportunity for rail transit I think, say for serving people commuting into SF, as well people traveling to the remote north coast for recreation. That whole area is really poorly served now, even bus service is scarce.
For anyone who's traveled in Japan, it's such a sad sight to see lack of high speed rail in California, and the main obstacle is obtaining the easements. So, I think both sides of this argument are understandable.
My first thought is to eliminate the binary logic. We don't just have 2 choices. Why not have both? Electric light rail with a pedestrian/bike path next to it...
The other example I gave replaced a railway that had been abandoned for a long time. I agree that rail needs a revitalization in the US, but at least here in Ohio, the problem is not right of way, but instead changing population patterns and competition from more convenient travel.
I'd love to take Amtrak to Chicago for a weekend trip, but it costs as much as a plane flight and takes longer than driving a car or riding in a bus. Fix that problem using the existing right of way, then we can talk about building more.
The coasts are a bit different.