Hi lynnfrbs1,
Welcome to the Mattress Forum!. 
Just in case you haven’t read it yet … the first place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly help you know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists (based on all the parts of your personal value equation that are most important to you).
[quote]- Flexus has recommended a 10’'mattress: medium-medium-soft for me and firm-firm- soft for my husband. IDLs are 22 soft, 31 med, 35 firm
- Bay Bed has recommended a 9’ mattress medium-soft-soft. and say that should be fine for both of us. IDLs are soft 24, med 23-27, firm 31
The IDLs are so different for both shops![/quote]
I think you mean ILD, not IDL.
You didn’t mention if the type of latex you’re comparing is the same in each layer of each bed, and if the blending is the same. But with that being said, the first thing to note is that you’re certainly comparing product that are using materials that are of a high level of quality.
The terminology used (“firm” or “soft”) is general, and the ILDs are a useful guide, but comparing one model from one brand to another is often futile, as different brands/manufacturers will source their latex from different producers, and these layers will have different feels for similar ILDs. While you’re not attempting to draw exact copies form one brand to another, it is important to note that even trying to compare different layers to another isn’t always especially useful, as a mattress is a complete system and you’re more concerned with the overall finished level of comfort.
The “softer” side configuration is actually a relatively similar design from both manufacturers. The difference would be more in the “firmer” side for your husband.
The only way to know for certain whether any specific combination of materials will be suitable for you or which ones you tend to prefer will be based on your own careful testing (hopefully using the testing guidelines in the tutorial) or your own personal sleeping experience because different people with different body types, sleeping styles, sensitivities, and circumstances can have very different experiences or opinions about whether the same mattress provides “enough” comfort and freedom of movement for their own personal preference.
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” or PPP (Posture and alignment, Pressure relief, and Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or if you can’t test a mattress in person then your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
Then, the most reliable source of guidance is always a more detailed conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart who can help “talk you through” the specifics of their mattresses and the options they have available that may be the best “match” for you based on the information you provide them.
As you’re aware, both Flexus and Bay Bed & Mattress are members of this site and I feel they compare well with the best in the industry in product knowledge, quality and service.
I look forward to learning about your decision after you go back and do some more reading and personal testing.
Phoenix