Hi MikeK,
The zones are symmetrical so they can be flipped and rotated.
They use a 7 zone 6" core and then separate comfort layers using Puralux (continuous pour Dunlop) and there is also latex quilted to the cover. They are very transparent about all the materials they use in their mattresses and I think very highly of Tom and the mattresses he makes. I was fortunate to be one of his “sounding boards” as he was developing his line of latex mattresses. Latexco doesn’t use any fillers in their latex.
Jamison uses Latex International for their talalay latex. LI does use fillers in their Talalay latex.
Latex of any type is among the most durable foam materials and I would have no durability concerns about either mattress … especially with your weight. You can read a little more about the factors involved in the durability of a mattress in post #4 here (and the posts it links to). I think you will find though that the Royal bedding is better value overall and would be more durable because it is realistically two sided (rather than having two different sides) but of course which one your testing indicates is more suitable for you and any extra cost involved in driving to Royal Bedding may of course also play a role in your decision.
Talalay is certainly not “better” than Dunlop (or vice versa) IMO and most of the online comments that you find saying one or the other is 'better" are usually promoting the type of latex that they sell and only telling part of the story. They are just different versions of latex with a different “feel” and properties. Some people prefer one while others prefer the other. You can read a little more about the different types of latex in this article and in post #6 here.
Phoenix