Hi MrMike,
This would depend entirely if any of the benefits of a thicker mattress are meaningful or apparent to you. There is no intrinsic reason to buy a thicker mattress if the benefits aren’t apparent to you. Post #14 here talks about some of the potential benefits of thicker mattresses and layers (assuming the materials are the same).
In some cases as well … thinner mattresses are set up on an “active” boxspring which could make a significant contribution to the feel and performance of your “sleeping system” so I would make sure that you are comparing apples to apples (mattresses that are on a firm non flexing foundation). If you test a mattress on a flexing foundation … then this should be part of the purchase so what you sleep on at home will be the same as what you tested.
Most of what you will hear in the industry is biased towards what a particular manufacturer sells (which of course is usually presented as being “better”). You can read more about the different types of latex and how they compare in various ways including durability post #2 here and in post #6 here along with post #6 here.
Overall … while Talalay and Dunlop are different in how they feel and perform … I would treat them as close equivalents in terms of durability (assuming all the other durability factors of the mattresses are the same because softer foams are also less durable than firmer foams) and blended Talalay and 100% natural Dunlop are usually fairly comparable in terms of price so the choice between them would be mainly about preference based on the differences between them rather than about “better or worse”.
You’re very welcome … I’m glad it could help you make the “best” choice for your criteria, preferences and circumstances 
Phoenix