Hi kelaenoptera,
Welcome to the Mattress Forum! 
That’s a long time to look for a mattress! Hopefully you’ve been able to use the information here on the site and in the Mattress Shopping Tutorial to assist you through this process.
One of the main things I talk about in that tutorial is that this site is set up to help with the “how” to choose, but not the “what” to choose, as it’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
And while other people’s comments about the knowledge and service of a particular business can certainly be very helpful, I would be cautious about using anyone else’s suggestions, experiences or reviews on a specific mattress (either positive or negative) as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you. In many if not most cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person in terms of comfort, firmness, and PPP may be completely unsuitable for someone else to sleep on (even if they are in a similar weight range). In other words, other people’s experiences in general won’t tell you much if anything about the suitability, quality, durability, or “value” of a mattress for any particular person (see post #13 here).
In its simplest form choosing the “best possible” mattress for any particular person really comes down to FIRST finding a few knowledgeable and transparent retailers and/or manufacturers (either locally or online) that sell the types of mattresses that you are most interested in that are in a budget range you are comfortable with and that you have confirmed will provide you with the all the information you need about the materials and components inside the mattresses they sell so you will be able to make informed choices and meaningful comparisons between mattresses and then …
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Careful testing (hopefully using the testing guidelines in the tutorial) to make sure that a mattress is a good match for you in terms of “comfort”, firmness, and PPP … and/or that you are comfortable with the options you have available to return, exchange, or “fine tune” the mattress and any costs involved if you can’t test a mattress in person or aren’t confident that your mattress is a suitable choice.
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Checking to make sure that there are no lower quality materials or weak links in a mattress you are considering relative to your weight range that could compromise the durability and useful life of the mattress (all of these look good for that).
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Comparing your finalists for “value” based on #1 and #2 and all the other parts of your personal value equation that are most important to you.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation (which it sounds like you’ve already done) with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc.) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences or to other mattresses that they are familiar with than anyone else. And at that time you can inquire about any potential exchange/return policies in case your purchase doesn’t turn out as well as you had hoped.
With all of that being said, I can make comments upon the brands that you listed regarding their componentry.
They use high quality materials - Talalay from Talalay Global for their blended or Radium for their natural Talalay latex. They are very knowledgeable about zoning and customizing their VZone system, but you are correct that you can save some money if you don’t think that zoning is necessary. The 100 day money back guarantee gives you a long amount of time to test out their product.
This line uses natural Dunlop latex, which overall can have a bit more of a “dense” comfort as compared to Talalay. While I wasn’t part of your phone conversation, if you still have unanswered questions I would phone back to make sure that any concerns you have are addressed. They also have a 100 day return policy.
As I posted above, while your friends are certainly well meaning, I wouldn’t use their opinion as a reliable indicator as to the appropriateness of this or any other product for your personal use. If your friends are close by, one good thing about them having this mattress is that you could go try it out personally. This product features natural Talalay from Talalay Global, and their upper layer on each side has “zoning” (differences in pinhole cores). This mattress is flippable, with each side having a different feel (Luxury Plush or Gentle Firm), so there is no choosing or customization here (unless you added a topper). They offer a 120 night sleep trial which is also good.
As you are aware, FloBeds and Sleep On Latex are members of this site, which means that I think very highly of them and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. While Saatva (ZenHaven) is not a member here, this mattress uses good quality components and certainly would be worth considering in this list.
The good news is that any of your choices are better than what the large majority of people end up purchasing and in terms of quality and value there are really no “bad choices” or “mistakes” left any more and when you are at this point and there are no clear winners between your finalists then the odds are high that any one of them would be a good choice that you would be happy with.
I’ll be interested in what you decide upon.
Phoenix