Hi hmorneau,
Dunlop and talalay are two different methods of making foamed latex and either of them can use ether natural or synthetic latex or a blend of the two. Dunlop is a simpler production process than Talalay so it tends to be less costly and natural latex is more costly than synthetic so the raw materials would also affect the price of the latex.
You can read a little more about the different types of latex post #6 here and there is also a little more about how Dunlop and Talalay compare in post #7 here.
The choice between then would be a matter of personal preference rather than a “better / worse” choice.
When a new mattress is significantly different from what your body is used to and your “sleeping memory” then it can certainly take a little longer to adjust to it and this wouldn’t be unusual at all.
Phoenix