Hi dsandys,
All of the options you are considering use good quality durable materials and there are no obvious weak links in any of them. The only “lower quality” material in any of them is the 1" layer of 1.35 lb polyfoam in the iChoice but this is inside the guidelines I generally use of “no more than an inch or so of lower quality or unknown foam” in a mattress and it is also deeper in the mattress (underneath 5" of latex) so it would be less subject to the mechanical stress of sleeping so both of these together means that it will have a negligible effect on durability.
I generally make “mattress only to mattress only” comparisons so that any differences in the type or cost of the foundations don’t skew the comparisons (any suitable foundation can be used under a mattress) but the two local options you are considering would both make good choices and I would choose between them based on the criteria of your personal value equation that are most important to you. In terms of the “material value” of both mattresses … the iChoice would probably have the edge because it has more latex inside it and also has a separate topper which can be replaced without replacing the whole mattress if that ever becomes necessary but these would be secondary to which mattress is the best “match” for you in terms of PPP because the quality of your sleep will be more important over the years than relatively small differences in price when you make the initial purchase … assuming both are inside a budget range you are comfortable with.
The 9" mattress from SleepingOrganic has both advantages and disadvantages. The disadvantage of course is that you can’t test it in person before a purchase. The advantage is that it has a zip cover with individual layers that can be customized and re-arranged or exchanged after a purchase if you need to do any fine tuning after you sleep on it and you can also replace individual layers down the road if it becomes necessary either because one layer has softened more than the others (usually the top layer) or your needs and preferences have changed over time. It also uses a more costly wool quilted cover for temperature regulation and as the fire barrier for those who would prefer it.
You are in a great position where your choices are all between “good and good” and there are really no “mistakes” in terms of quality so the final choice that is best for you will really depend on which one is the best match for all the objective, subjective, and intangible criteria that are most important to you.
Phoenix