Hi rosscohen,
The first thing I would suggest is to read post #1 here which has the basic information, steps, and guidelines that you will need to make the best possible choices (and avoid some of the lower quality or value choices like the two you are looking at).
A mattress is only as good as its construction and the quality of the materials, components, and foam inside it regardless of the manufacturers label that is on it so to make any meaningful comparisons between mattresses in terms of quality or value you would need to find out the quality specs of the layers and components inside it. You are not likely to find this with Shifman except perhaps in generic terms (that doesn’t include the quality of the materials) and I wold personally not consider a mattress where you can’t validate the quality of the materials it uses … which usually indicates that they are lower quality than other mattresses in similar or lower price ranges.
You will probably find that the comfort layers of the RoomandBoard mattresses you are looking at (which are the weak link of most mattresses in terms of durability) are low quality polyfoam in the 1.2 lb range which means I would avoid these as well but I would confirm this with them before excluding them.
You can’t “feel” the quality of the materials in a mattress or know it by the price of the mattress and both low quality and high quality materials can feel great in a showroom. The difference is that higher quality materials (regardless of the price of the mattress or the manufacturers label) will last longer and stay closer to its original feel, comfort, and support over a longer period of time.
While the Washington, DC area is not the best in terms of its selection of good quality and value mattresses … the better options and possibilities I’m aware of are listed in post #2 here.
Phoenix