Hi AnalogJ,
I don’t have any personal experience with any of them (although I do use the NaturaProtect Deluxe which is similar except it has a semi breathable waterproof membrane … and you can see my comments here). Some of the differences between them would be more subjective based on how they would “feel” but these types of products are much more difficult to compare on a more objective or “commodity” basis. The obvious differences would be in the oz/yd of wool (which would have a significant effect on the cost), the thickness and quality of the cover, any organic certifications, the cost and quality or breed of the raw wool, the finer details of the construction (such as finished edges or quilting patterns), and the time and labor involved in making each one (and the labor costs in the country of origin) along with the normal differences between the pricing policies of different businesses.
In most cases I would make these types of comparisons based on a conversation with each retailer or manufacturer and asking them to compare their product and price to the others you are considering so they can describe any significant differences in the materials, quality, or “feel” of their product compared to the others and you can make a choice based on the information they provide you.
Phoenix