This whole question has the air of an experiment.
While there will be opinions about the desirability or not of having the pRB spiral (or 2/3/4 ring binder) bound, only time will determine the durability of either the original format or subsequent user re-bindings. So while some, like me, don't want the hassle of re-binding it, others really like the idea of it laying flat, until all have had and used the pRB for 6 months to a few years, nobody can really say which format lasts or is sufficiently durable.
Await the experimental data!