Hi dhanley,
All of your finalists have a similar design and I would agree that you’ve reached the point where any of your finalists would be a good choice.
The only additional comment I would make is that a 6" latex mattress would also be more than enough for a child and would probably be fine for an adult on occasion as well (and for some adults may also be fine on a more regular basis) and this would also lower your costs although 9" may be more “comfortable” for most adults on a more regular basis.
I would make your final choice based on your phone conversations with each of them along with all the objective, subjective, and intangible parts of your personal value equation that are most important to you. I don’t think you could go wrong with any of them.
Phoenix