Make Sure Your Mattress Is Made For You
Your mattress must support you meaning have the ability to keep your spine aligned in all your sleeping positions. It is very important with the thousands of choices in the mattress world, you make sure you choose the best mattress for you. You are looking to see if your spine is straight when you are on your side or follows its natural "S" curve when you are on your back or stomach. When you have 2 - 3 mattresses that seem to provide the best support and alignment, then its time to go home and compare the mattresses to see any common patterns in the ones that worked best for you.
If any "parts" of you sink in too much (usually pelvic area) or too little (usually shoulder area) then you will sleep out of alignment which usually leads to pain or discomfort in the lower back, upper back, or neck and shoulders (which can also be from the wrong pillow for your sleeping positions). It also helps to "stand up straight with good posture" before you lie down on your back or stomach so they can "memorize" what your natural "S" curve looks like and see if it looks the same when you are lying down. You should also there are no "recessed areas" in all sleeping positions to make sure that they are being "filled in" and supported. If it is too easy to slide a hand under then it means that the mattress support layer could be too firm to allow for good support and alignment. If you are "hammocking" and the heavier parts are sinking down too far then this too can means poor support and alignment. Pay particular attention here to make sure that the pelvic area isn't sinking down too far, that the shoulders are sinking in far enough, and that the head and neck are in alignment (always test a mattres using a suitable pillow).
The best mattress for you is all about personal preference and your bodies physical needs. You could choose ultra-firm (hopefully not) and to ultra-plush, it is all about making sure you have the back support with the right combination of padding to make you feel comfortable.
For you stomach sleepers, medium firm to plush mattresses provide the perfect blend of comfort and support.
Stomach sleeping places pressure on sensitive areas like your chest, face, and elbows. A mattress that is too soft can allow your lower back to sag downward or place added tension on your neck. But, a mattress that is too firm can also cause pain and pressure points. Your ideal mattress is in the medium range, with a supportive comfort layer. Your back shouldn’t feel strained or tense when you lie down. It may also be helpful to place a pillow beneath your hips to prevent your lower back from sinking too far (however, lets try to find one that does not require that).
From my experience in the variety of Portland mattresses out of all those in the mattress world, the more curvy you are the more padding needed to fill the arch in your back and the behind your neck as well as the spaces behind different parts of your legs. Back sleeping places most of your body weight on your upper back, bottom, and heels. A bed that is too firm and rigid can cause pressure points and leave your lower back unsupported, contributing to muscle tension and pain. A bed that is too soft can also lack support or allow your upper body to sink too far in, also contributing to discomfort.
Please make sure you make you get support if you sleep on your back also. It is the best way to sleep, and often if you have medical issues it is required. Your ideal mattress is likely in the medium to medium-firm range, with a comfort layer just thick enough to cushion pressure points, but not so thick or plush that your upper body sinks too deep. You should not be able to fit more than 1 finger between your lower back and the mattress when lying flat.
You Found Support, Now Go For Comfort
It is best to get most of the comfort from the core and contouring, because the comfort layers will flatten out over time. Comfort is a combination of the support system and the layers on top. The more expensive beds tend to build up the core for longevitiy. This is perhaps the most simple and straightforward of selecting the best mattress and is where you choose between different mattresses that have the "feel" you like, good pressure relief, and good spinal alignment and compare them based on quality and durability.
Mattresses break down from top to bottom so make sure you have a great core and quality on top of that. Your choices would be simple if they all were roughly the same cost or even if there cost was just a little more since it is clearly a higher quality mattress and would be much more durable. This is your focus on long term satisfaction with your mattress so you won't find you are one of those who loves your mattress in the store and for a few months after only to discover you made a mistake.