Hi dfisher,
You are finding lots of “Beautiful” options 
While I can’t tell you what to do because your criteria or risk tolerance may be very different from mine … I would keep in mind that if there are any defective materials in a mattress they are likely to show up in the first year or possibly two and after that the quality of the materials is much more important than the length of a warranty. I also wouldn’t “expect” any mattress to last for 20 years because in many cases your own changing needs and preferences (we all “age” unfortunately) may be the limiting factor in how long a mattress is suitable for you. I would treat anything more than 10 years as a “bonus” although you are much more likely to have “bonus time” with latex than with other materials.
While I also can’t read the future … it would surprise me if Latex International went out of business.
Other than that when you are looking at a final choice between “good and good” and when there are no clear winners between them I would choose the one that you feel most comfortable dealing with or that you find that you are leaning towards most strongly since it’s almost 6 of one and half a dozen of the other and neither one would be a “mistake” IMO.
Phoenix