Hi geearle,
This would depend entirely on how well each mattress matches your needs and preferences in terms of PPP (Posture and alignment, pressure relief, and Personal preferences). My guess is that since both of these are fairly firm that you would likely need a topper for both of them (unless your testing confirms that one or both of them work well without a topper). The suitability of a mattress in terms of PPP is just as important as durability because if a mattress is very durable but not suitable for you then you wouldn’t be able to sleep on it no matter how durable it was.
The Embody Insightful has 3" of smart latex in the top layer which is mostly synthetic latex but is more durable than polyfoam. The Riverview Villa firm has some high loft fiber and then 1" of polyfoam above the smart latex in the comfort and support layers. While both of these would be among the better options for an exchange where you were looking for a base mattress and planned to add a topper for pressure relief and comfort … the Riverview firm (not cushion firm by the way which is different) has lower quality polyfoam and fiber in the upper layers that would be more subject to softening and impressions over time than the latex in the Insightful so I would give the edge in terms of durability to the Insightful even though it has a lower quality polyfoam support layer.
The risk of a mattress/topper combination is that it can be difficult to choose the best topper unless you have tested them together. If you exchange for a mattress without the topper (and buy the topper elsewhere), then the topper guidelines in post #2 here and the posts it links to will be helpful. The benefit of a topper is that it can be easily replaced if it softens or breaks down faster than the mattress and you can replace it at a much lower cost without replacing the entire mattress.
Phoenix