Hi kimbeck,
You are certainly looking at some good quality/value options 
[quote]1) Can return free within 30 days (if purchased through Amazon Prime). After that I think you’re pretty much stuck with it.
I also like the possibility of it getting here in 2 days and being able to return it for free.[/quote]
I would confirm the cost of returning a mattress through Amazon (when they fulfill the purchase) because I don’t believe that the returns are free. There is a lot of confusion about just what their return policy is because they ship many of their mattresses compressed through UPS but if you return it, it has to be shipped through common carrier (truck freight) which is much more expensive and their large items department handles the returns in this case. When I talked to them about this they told me they deduct return shipping from your refund and the charge for large item shipping is 5.99 per lb and an additional fee of 4.99. This means that a 100 lb mattress would cost $603.98 to return. When I asked them (the large items department) about this they told me that the return fees would be “capped” to about 20% of the cost of the mattress … assuming that the mattress was in pristeen condition and being returned within the required timeframe. It may be worth talking to them to confirm this to see if they provide the same information to you because I would want to know for sure before I ordered a mattress through them (their cost is also slightly higher than ordering the same mattress fulfilled by Dreamfoam). They also told me that sometimes they will offer a refund of $50 and let you keep the mattress rather than losing money on a return and then you can sell the mattress for what you could get on Craigslist. I would make sure you only talk to the large items return department because their regular customer service people may give you incorrect information about returns for a mattress that was shipped compressed.
The customer service people at Dreamfoam (and other good manufacturers and retailers) will generally provide you with good information that they legitimately believe would be in your best interests regardless of how it benefits them financially. Thicker mattresses can be more adaptable to different people and different sleeping positions than thinner mattresses (see post #14 here) so the Eurotop could provide more “contouring” and adaptable support that would certainly be noticeable for some people. The Eurotop also provides the option to exchange the comfort layer at a minimal cost so this may also be important to you unless you are completely confident in your comfort choice. It would also provide the option of changing the comfort layer down the road if your needs or preferences change without having to replace the entire mattress.
Overall though … when you are comparing “good vs good” then which of your final choices would be “best for you” would really depend on the parts of your personal value equation that are most important to you regardless of whether someone else may have the same criteria or make the same choice.
The Morgongava uses 85% natural and 15% synthetic continuous pour Dunlop latex while the Latex International Talalay is about 30% natural and 70% synthetic. Both of them are very “safe” materials and would provide good durability. There is more about the different types and blends of latex in post #6 here but the most significant difference between them would be the difference in the “feel” and resilience of Talalay latex vs Dunlop latex (see post #7 here).
Phoenix