Hi bobheist,
The type of quilting layer used in a mattress (latex or otherwise) is really a matter of personal preference and isn’t a durability factor if it’s in the area of “around an inch or so” or less. It can have a positive or negative effect depending on the preferences of each person. There is more about the pros and cons of different types of quilting layers and unquilted covers in post #2 here and the posts it links to.
You can read my thoughts about a mattress purchase from Costco in post #4 here.
Most local retailers or manufacturers don’t have a refund policy but this is much less important when you can test the mattress in person and you know the quality of the materials … especially if there is an exchange policy that has many good options available (although both a refund and exchange policy are built in to the cost of a mattress purchase because the people who don’t exchange or refund pay for the ones who do).
I’m not sure which prices you are using but both the Caress and the Sleep Science are in higher budget ranges than other similar online mattress choices you have (some of which also have a good refund policy) and there are fewer options to fine tune the mattress after the purchase as well than you would have with a component mattress where layers can be rearranged or exchanged. Post #21 here includes the list of the members here that sell online and it includes a wide range of component latex mattresses that use a range of different types of latex and have many different features, choices, options, and price ranges (many of which are lower cost than both of the options you are considering).
The Sleep Science latex uses 9" of blended Talalay latex so you can use this as a reference for comparison. You can read more comments about it in post #2 here.
There is also more about the Costco Nature’s Caress latex mattress in post #4 here and for comparison purposes it uses 10" of blended Talalay latex.
The Parklane Overton uses 100% natural Talalay in the 6" core which is a more costly version of Talalay and is also significantly less than either of the Costco options you are considering.
Phoenix