Hi Hfaust245,
Welcome to the Mattress UnderGround and Happy Holidays.
Choosing between the medium and firm versions of the DLX Classic mattress largely depends on your preferences for support and comfort, particularly as side sleepers. For example I am 6’ 220 and wife is 5’4 135 and we sleep on a Plank Luxe, a much firmer mattress. No issues at all, and love the sleep on top of the mattress firmness. I have experimented with a few different toppers over the past 2 years with this mattress, not necessarily for the comfort aspects, but just to try different toppers to be able to speak about the experience first hand.
Since you mentioned that your current mattress is dipping at your hips, this could always be a concern to address with the any new mattress. With a DLX, that is unlikely. Like any product out there, the better the quality, the more logical and thought out construction, the better the chances of experiencing compromising issues.
A firmer mattress (DLX Classic Firm) generally provides better support for your hips and lower back, reducing the likelihood of sinking too much into the bed, which could help prevent further back pain. Since I tend to favor leaning firm on a mattress, and supplementing with a topper if necessary, that would be my recommendation. Your own personal experiences can help guide you, but it is clear you have had some experiences already. You BR is only 4 years old and you are experiencing some issues, these two videos BeautyRest Black, and yet another. As you can see, it doesnt matter which series. Many of them have the same issues. As mentioned in the videos and your own experience, it is not a happy place to be as both videos explain why.
If you feel like a firm mattress would be too uncomfortable for your shoulders, the medium version may strike a better balance between support for your hips and comfort for your shoulders. The one thing you will no have to deal with here is the fact that a good quality mattress will have that balance of support necessary for support and a logically constructed comfort layer, that with have the right amount of cushion so you are not sinking like the titanic.
Regarding warranties, here is a conversation I had earlier this year on the Mattress Underground with someone who worked for a warranty company. So, good luck with that.
One reason I had to buy my mother-in-law a DLX Premier Hybrid earlier this year is that her Beautyrest mattress failed dramatically in less than 15 months. She was experiencing intense pain in her hip and lower back area on top of her existing geriatric ailments. Upon inspecting her mattress, it seemed that the entire comfort layer and cover had sunk down to the springs. She had paid for an extended warranty through Raymour, but knowing the process and not wanting to deal with the time-consuming steps—emails, photos, phone calls, etc.—and never being certain of the outcome, I just decided to order a DLX for her. Less than a week later, it was delivered to her home, placed on her new Yawnder4 adjustable base, and she was finally sleeping comfortably again.
You don’t want to spend the rest of your life dealing with a mattress inspector who will keep moving the goalposts until you give up.
I am sure @DLX may chime in with their professional assessment too, and for the record, they tend to be modest, as they are not the type to over promise, but their products are extremely well made, durable and provide comfort and longevity. If you do decide to go with the firm, their comfort layer and cover will still offer a nice balanced cushion affect.
Hopefully this helps,
Maverick