Hi planetship,
I would keep in mind that “support” and “comfort” are both relative and can vary based on the body type, sleeping style, and individual preferences of different people. A mattress that is “perfect” for you may be completely unsuitable for someone else to sleep on regardless of the specific materials and components in a mattress.
“Support” is often misunderstood because the goal of a “supportive” mattress is to keep the spine and joints in good alignment and this requires the type of contouring support that allows some parts of the body to sink in more (softer) and some parts of the body to sink in less (firmer) and this will vary on an individual basis based on body type and sleeping style. There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support/alignment” and “comfort/pressure relief” and “feel” and how they interact together.
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). The best way to know which type of materials or which type of mattresses you (or someone else) may tend to prefer in general terms will be based on your (or their) own careful testing and personal experience because different people can have very different preferences.
I would certainly agree with you here in general terms. The major brands such as Sealy/Stearns & Foster, Simmons, and Serta all tend to use lower quality materials in their mattresses than most of their smaller competitors that will tend to soften or break down prematurely relative to the price you pay which is why I would generally suggest avoiding all of them completely (regardless of how they may feel in a showroom) along with any mattress where you aren’t able to find out the type and quality/durability of the materials inside it (see the guidelines here along with post #3 here and post #12 here and post #404 here).
I would completely disagree with you here. Many local stores carry mattresses that aren’t available online and while I would avoid the major chain stores (that tend to focus on major brand mattresses) … there are local retailers or factory direct manufacturers in most areas of the country that sell great quality/value mattresses that are certainly in a similar “value” range to online manufacturers … you just need to know how to find them. Local testing also gives you the chance to test and compare many different mattress in person and in “real time” to see which of them are the best “match” in terms of comfort, firmness, and PPP while purchasing an online mattress doesn’t give you the chance to compare the mattress you are purchasing with other mattresses (unless you have tested that specific mattress in a store).
Online retailers and manufacturers and local retailers or manufacturers each have their own pros and cons but I certainly wouldn’t say that one was inherently “better” than the other because this will depend on the specific retailers or manufacturers you are considering and on the risk tolerance and the specific criteria that are important to each individual person. Your risk tolerance and criteria and all the parts of your personal value equation that are important to you may be very different from someone else.
Phoenix