Kudos on narrowing your search to Jamison Mattresses because I believe whole heartedly about the quality and craftsmanship put into each Jamison Mattress.
This is intended to be advice from being around Jamison for many years, but please remember, ALL Mattress feels are subjective. Meaning that a Mattress that feels good to me, may not feel good to you, and vice versa. I will base my suggestions on the Jamison Mattresses that get the Best Reviews or positive customer experience.
Also, it will depend on the price range you are willing to pay for a good nights sleep. I will not be able to put exact prices on the selections as it goes against Jamison's terms of service.
Ok, get on with it right! If price is not a barrier, there are 2 selections that always get great reviews and feel great from day one. The Jamison Lady Lark which is an All Latex Mattress with a 20 year warranty in the popular Jamison Resort Collection. This is a top of the line Jamison model, but other Mattress makers have mattresses that are much higher in price. I don't want to scare you about price because it is very affordable when you put it into perspective.
The 2nd Best Reviewed Jamison Mattress, not necessarily in that order would be the Jamison LaJolla, also in the resort Collection. This is a newer model, but early Reviews on this Mattress, place it at the top. That is my 2 top choices, but if you are on a budget, there is also a Jamison Mattress for you that gets amazing reviews. The Sunflower Plush and Sunflower Euro Top Mattresses will not break the bank and their pocketed coils feel like a much more expensive mattress set.
That is my suggestion for Jamison Mattresses that receive Great reviews and have been staples for the Jamison bedding lineup. Do not let me forget, if you are looking for a mid price mattress, be sure and check out the Aphrodite Plush or Aphrodite Firm selection which are both 2 sided, or can be flipped. This is a Mattress that were made years ago that lasted forever. A large portion of readers are probably sleeping on a set made similar to these, and it is hard to find a 2 sided mattress with all the added expenses of production.
Jamison Bedding is the oldest Family owned Mattress Manufacturer in the US so whichever selection you choose, I feel you will be happy. This is the best advice I can give you on buying a mattress, find a company that has been in business long term, then find a Mattress that meets your budget, then pick the one that feels best. Since you are reading about Jamison Mattresses, your first and most important decision is well under way.