Hi Derek,
I’m surprised you are having difficulty finding out all the specifics of the foam densities and thickness in the OMF mattress because they have a book that they all have access to that includes them although they have multiple outlets and all the salespeople at every outlet may not be as helpful as others … especially in their lower end mattresses. Sometimes salespeople forget that even when they provide great service on a lower end mattress purchase it can result in many referrals and “work of mouth” advertising.
Restwell should also be able to provide you with their foam densities when they are open.
I would tend to use 1.5 lb polyfoam as a minimum for a lower end mattress (1.8 lbs with higher budgets or a two sided mattress) with the exception of a relatively thin layer in the range of an inch or so which won’t have a significant effect on the durability of the mattress and is mostly for “feel”. Depending to some degree on the body type and sleeping style of the person on the mattress, 1.2 lb polyfoam is low quality and can soften very quickly. Even if it’s not actually worn out, the loss of comfort and support (with or without actual visible impressions) can mean the mattress may need to be replaced quite quickly or you would need to “tolerate” a mattress that was no longer the best match for your needs and preferences.
There is more in this article and in post #10 here about the different types of innersprings but the only meaningful way to compare innersprings is based on “active steel” or the weight of the steel it uses and this isn’t information that any manufacturer I’m aware of provides. Other than that … the type of innerspring will have more to do with how a mattress feels and performs than with the durability of the mattress and in most cases the foams above the springs will be the “weak link” of a mattress although lower coil count innersprings with more “space” in between the coils also need a good quality insulator to even out the feel and response of the coils and prevent the foam and other materials from sinking into the gaps in the coils and making the mattress “lumpy”. OMF does use a good quality 13 gauge Bonnell coil and good quality insulators although it’s at the lowest range of a Bonnell coil count I would use (see here). The RoomandBoard uses an offset coil with a thinner 14.5 gauge wire but has more coils and they don’t mention the number of turns in each coil.
There are also a few other smaller manufacturers in the area that would be worth considering (or at least calling to see what they have available in your budget range) but of course that would depend on the time you have available and the travel distance to visit them.
I don’t know the delivery options they each provide but post #2 here has some options that may be useful if you need to dispose of an old mattress outside of the actual delivery process.
Phoenix