Hi Tourguide,
Welcome to the site … and I’m glad you found us 
[quote]We purchased a memory foam mattress 6 years ago and loved it - well, at least for the first 4.5 years. Over the course of the last year or so, we have been tossing and turning throughout the night. Since the mattress was only 4 - 5 years old, we didn’t think that could be the cause of our poor night’s sleep. For a while we attributed it to getting older but of late we have been waking with aches and pains in our shoulders and hips.
We have finally realized that it was the mattress. With a bit of research, we have decided that memory foam is not the answer but perhaps Latex is. We have a few questions we hope someone can assist with:[/quote]
I’m not sure of the specifics of the memory foam mattress you purchased but it’s possible that it used lower density memory foam which could be the reason that it only lasted you for 4 - 5 years. If you slept well on your mattress for 4.5 years it’s certainly possible that a more durable memory foam mattress could be a good choice.
Assuming that the materials in a mattress you are considering are durable enough for your body type and meet the quality/durability guidelines here relative to your weight range … the choice between different types and combinations of materials and components or different types of mattresses are more of a preference and a budget choice than a “better/worse” choice (see this article).
Latex and memory foam are very different materials with very different properties but the choice between them is more of a preference and budget choice than a “better/worse” choice. There is more about some of the differences between memory foam and latex in post #2 here but the best way to know which type of materials or mattresses you tend to prefer in general would be based on your own careful testing and/or personal experience with each material in a range of different firmness levels.
Dunlop and Talalay both come in a wide range of firmness levels so either one can be firmer than the other depending on its specific firmness but if both of them are the same ILD (and the ILD is measured in the same way which isn’t always the case) then Dunlop would tend to “feel” firmer because it has a higher compression modulus than Talalay (it gets firmer faster as you sink into it more deeply).
There is also more about some of the differences between Talalay and Dunlop in post #7 here but the best way to know which type or blend of latex you tend to prefer will be based on your own local testing and/or your personal experience. If you let me know your city or zip code I’d also be happy to let you know about the better options or possibilities I’m aware of in your area so you can check to see if there are any Talalay latex mattresses available to test in your area.
Any type or blend of latex (either Dunlop or Talalay and made with synthetic rubber, natural rubber, or a blend of both) is a high quality and durable material so the choice between them would also be more of a preference and a budget choice rather than a “better/worse” choice. There is more about the different types and blends of latex in post #6 here. Softer versions of any material would tend to be less durable than firmer versions of the same material.
Latex in general (both Talalay and Dunlop) is “good” with motion isolation because it’s a very point elastic material that can compress in one area with little effect on the surrounding area but it’s not as good as memory foam which is “excellent”. The specific design of a mattress will have more to do with motion isolation than the type or blend of latex but there is more about latex and motion isolation in post #4 here and there is more about motion isolation in general in post #18 here.
I’m looking forward to finding out what you end up deciding … and of course to any other comments or questions you may have along the way.
Phoenix