Hi Vic,
Many of them offer their customers a choice of the type of latex they would prefer in their mattress so you aren’t restricted to only a single choice (Habitat for example uses 100% natural Dunlop in their base layers and blended Talalay in their top layers). You can read a little more about the different types of latex in this article along with post #6 here and post #6 here and some of the differences between natural and synthetic rubber in post #2 here. In general the types of latex you would normally choose between are organic Dunlop, 100% natural Dunlop, blended Dunlop, 100% natural Talalay and blended Talalay. Each of these has their own pros and cons.
Most of them also offer a choice of firmness for the base support layer as well as the comfort layers.
Many of them are also component mattresses where the mattress is made up of layers that can be rearranged or even exchanged for a softer or firmer choice without having to exchange the whole mattress so you can fine tune your choice after a purchase. Different manufacturers on the list have different degrees of ability to customize their mattress.
Two of them (FloBeds and Custom Sleep Design) also offer customized zoning options.
There is also a wide range of prices and designs.
What they all have in common is that each of them in their own way is among the best value in the country and beyond that I don’t differentiate between them in terms of “value”. They are all very experienced and knowledgeable and have good service.
All of them are also very open and transparent about their materials and mattresses and are happy to spend time on the phone with you explaining their options and how they may benefit you. I would encourage you to talk directly with the ones that interest you the most because they know more about their mattresses and the options they offer than anyone else (and in some cases all of their options aren’t on their websites because some of them offer customized choices as well).
A forum search on Plushbeds (you can just click this) will bring up many comments about them and some comparisons with some of the other manufacturers on the list.
A forum search on Habitat (you can just click this as well) will also bring up many posts and some comparisons with them as well.
I’m happy to help the members here with “how” to choose but the specifics of what to choose and your own final choices will always depend on your personal value equation and which of the objective, subjective, and even intangible differences between them are most important to you.
Any of them would make a great choice but as you narrow them down based on your own criteria and conversations one of them will end up being the best choice for you 
Phoenix