I can't directly answer your question, but I can say that I found that Swiss hotel websites don't have all the rooms available on their own booking engines. I had to e-mail hotels to get the rooms I needed (and in 2 of the 3 cases, got a Rick Steves discount as well). So, if you are going without reservations, be sure to call the hotels directly or visit them in person - don't just go by what's shown on their website.
In general, in these days of advance booking being very easy with e-mail and Internet, the best rooms in each price category tend to get taken, and those without reservations get what's left over. Of course that is a generalization, and for some places it's not a problem, and if you have a car you can always head down the road to find a room. But if you have your heart set on being in a specific place at a specific time, it's best to reserve.