Hi Saphireblue,
While I can certainly help with “how” to choose … I don’t 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” or PPP (Posture and alignment, Pressure relief, and your Personal preferences) 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 accurate 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).
There is more about the 3 most important parts of “value” of a mattress purchase in post #13 here 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 suitability, durability, and all the other parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
There is also more information in post #9 here about the different ways that one mattress can “match” or “approximate” another one. Every layer and component in a mattress (including the cover and any quilting materials) will affect the feel and performance of every other layer and component and the mattress “as a whole” so unless you are able to find another mattress that uses exactly the same type of materials, components, cover, layer thicknesses, layer firmnesses, and overall design (which would be very unlikely) then there really isn’t a way to match one mattress to another one in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your Personal preferences) based on the specifications of the mattresses (even assuming that you can find out all the specifications you would need for both mattresses you are comparing).
Mattress manufacturers generally try to differentiate their mattress from the mattresses made by other manufacturers and don’t normally try to “match” another mattress that is made by a different manufacturer so unless a manufacturer specifically says in their description of a mattress that one of their mattresses in the same general category is specifically designed to “match” or “approximate” another one in terms of firmness or “feel” and PPP and/or they are very familiar with both mattresses and can provide reliable guidance about how they compare based on the “averages” of a larger group of people that have compared them (different people may have very different opinions about how two mattresses compare) … the only reliable way to know for certain how two mattresses would compare for you in terms of how they “feel” or in terms of firmness or PPP would be based on your own careful testing or actual sleeping experience on both of them.
You can read more about Pranasleep in general and the previous versions (up to version 4) of Pranasleep mattresses in post #3 here and in post #2 here and in post #3 here and in posts #1 and #2 here and a forum search on Prana (you can just click this) will also bring up more information and feedback about them as well.
The good news is that they changed the design in version 5 and the top layers of polyfoam are now higher quality/density and are no longer what I would consider to be a weak link in the mattress in terms of durability. Having said that they are still in a significantly higher budget range than other similar mattresses and the top layers are still polyfoam so you would still be feeling and sleeping on polyfoam as much as latex but this could also be a “feel” that you prefer compared to sleeping more directly on latex . There is more about the new version 5 in post #19 here but I would certainly make some very careful “value” comparisons with other latex mattresses that use similar materials and are in a lower budget range before considering one of their mattresses to be the “best value” choice available to you.
While there is no way to quantify how long any mattress will last for a specific person or predict exactly when you will decide to replace it because it is no longer suitable or comfortable for you (because this is the only real measure of durability or the useful life of a mattress that really matters) because there are too many unknowns and variables involved that are unique to each person … if a mattress is well inside a suitable comfort/support range and isn’t close to the edge of being too soft when it is new (see post #2 here) and you have confirmed that it meets the minimum quality/durability specs that are suggested in the guidelines then it would be reasonable to expect a useful lifetime in the range of 7 - 10 years and with higher quality and more durable materials like latex or higher density memory foam or polyfoam (in the comfort layers especially) it would likely be in the higher end of the range or even longer and the chances that you would have additional “bonus time” would be higher as well.
There is also more detailed information about the many variables that can affect the durability and useful life of a mattress in post #4 here.
If a mattress uses lower quality/density materials than the minimum in the guidelines and there is a weak link in the mattress then it would be reasonable to expect that it would last you less than this … and in some cases it could be significantly less. I would consider it to be “lucky” if it lasted you for 10 years.
The industry has changed a lot in the last 20 years and all the major brands (such as Sealy/Stearns & Foster, Simmons, and Serta) 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 and I would generally suggest avoiding all of them completely 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).
You may have seen this already but just in case you haven’t … the better options or possibilities i’m aware of in the Washington, DC/Northern Virginia area (subject to making sure that any mattress you are considering meets your criteria and quality/value guidelines I linked earlier in this reply) are listed in post #2 here.
Phoenix