Hi AnalogJ,
There are a lot of variables when you are comparing two wool products including the type and breed of wool, the amount of wool in each one, how the wool is compressed and quilted, and the type of fabric that covers it, and I think this is really only possible to answer based on your own personal preferences and experience and why you are considering one over the other … especially when you already have a wool topper on your mattress.
I suspect that either one would likely be fine since you already have a wool topper on top of your mattress and seem to like the “feel” of thicker wool layers but in very general terms thicker layers of wool will modify the effect of the mattress or foam materials underneath them more than thinner layers.
I believe the 45th St Bedding uses 10 oz/yd of wool. You can see my comments about washing and drying my Queen NaturaProtect protector which also has 10 oz of wool in this post. It’s a full load.
Phoenix