Hi bobby2478.
Thanks for providing the stats and sorry to hear that your previous memory foam mattress has caused you back pain.
You are on the right track with selecting beds with good quality and durable componentry. Generally speaking, you can do well with either of the options you listed as there are no “real downsides” to any of them. Everything boils down to the PPP (Posture and alignment, Pressure relief, and Personal Preferences). There are many complex differences in how they “feel” within each category and the best way to decide is to ensure that your PPP is met. Other than this innersprings are less costly than quality latex and both innersprings and a firmer latex core can be used as a support layer and each has very “different” characteristics but the most important differences are the ones you can feel and that you personally prefer. Both can be softer or firmer depending on design so a pocket coil could be firmer than a latex core or the other way around they could be zoned or not all depending on the specifics of the components you are comparing. There are quite a bit of resources about this in post #10 here and more detailed information about innersprings vs latex support cores in post #2 here and more about the different types and blends of latex in this article and in post #6 here or post #29 here
Your “initial thought” is good especially as you are both combo (back/side) sleepers. I always suggest to do the due diligence but back it up and trusting your gut feeling in cases like this. Some theory at a distance might help with knowing what to focus on in terms of characteristics and differences between the two or to see if it worth taking a trip to test try one … but generally speaking unless there is something that completely disqualifies a certain mattress type… personal experience is the best way to assess if you like the general feel of it.
In your selection process a few things you may want to keep in mind
• Thinner upper layers will bring the lower layers (such as an innerspring) more into play and may change what works best and is most durable (such as in mattresses where the coils themselves are a big part of pressure relief") but it is the balance and interaction between all the layers that result in the end product and creates the overall durability of the mattress.
• Pressure-relieving qualities (come from the pressure-relieving cradle upper layers form which spreads your weight out over the mattress surface),
• Posture and alignment qualities (which is the ability of a mattress to “allow” your wider lighter areas like shoulders to sink in enough while “stopping” the heavier narrower areas like the pelvis from sinking in too far) which keeps your spine in alignment in all your sleeping positions,
• Preference qualities (are very unique and subjective to each individual and preference-based like breathability, being more “on” or “in” the mattress springiness, energy absorption, the surface or “hand” feel of the mattress, motion isolation, slower or faster response, and others).
Hopefully, this gives you a bit more food for thought and confidence to take your next step
Phoenix