[quote]1: learn enough about mattresses to be able to assess the trustworthiness and competence of a retailer.
2: trust them.[/quote]
The return/exchange options you have available will also be an important part of the “value” of a mattress purchase if you aren’t confident that a mattress will be a good “match” for you in terms of comfort, firmness, and PPP. I would also keep in mind that if you are dealing with a reliable manufacturer or retailer that it’s in their self interest to help you choose a mattress that is a suitable choice because no reliable business would choose to have a customer that is unhappy with their purchase.
In a word no. Unfortunately (and regardless of someone’s level of expertise or experience) nobody has a crystal ball that can predict for certain which specific mattress or combination of materials you will like best or that you will sleep best on … it just doesn’t exist.
I or some of the more knowledgeable members of the site can help you to narrow down your options, help you focus on better quality/value choices that are available to you either locally or online, help you identify any lower quality materials or weak links in a mattress, act as a fact check, answer many of the specific questions you may have along the way that don’t involve what you will “feel” on a mattress, and help with “how” to choose but only you can decide which specific mattress, manufacturer, or combination of materials is “best for you” regardless of the name of the manufacturer on the label or whether anyone else (including me) would have the same criteria or circumstances or would make the same choice.
I would keep in mind that there are no “standard” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness and some people may rate one mattress as being firmer than another and someone else may rate them the other way around. This is all relative and very subjective and is as much an art as a science.
Assuming that the materials in a mattress you are considering are durable enough for your body type and meet the quality/durability guidelines here relative to your weight range … the choice between different types and combinations of materials and components or different types of mattresses are more of a preference and a budget choice than a “better/worse” choice (see this article).
Every category of mattresses (including innersprings, latex or memory foam mattresses) can include hundreds or even thousands of different mattresses with different designs, different “feels”, different characteristics, and different firmness levels. Every layer and component in a mattress (including the cover and any quilting material) will affect the feel and response of every other layer both above and below it so each category will generally include some mattresses that will be a good “match” for you in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own personal preferences) and others that use the same type of materials and are in the same category but have a different design that may be very uncomfortable and may be completely unsuitable for you to sleep on even if the actual materials are the same. Whether a mattress would be a suitable choice in terms of PPP will have more to do with the specific design of the mattress than the materials inside it which is just a preference … not a “need”.
Testing and comparing a range of local mattresses in “real time” can give you a sense of how you feel about different materials or different types of mattresses in very general terms if you can identify “patterns” in your experience but the only way to know for certain whether you like a specific mattress or whether it will be a good “match” for you in terms of “comfort”, firmness, and PPP will be based on your own careful testing or your personal experience.