Hi newkidontheblock.
Yes they will feel different. While your own testing is the most reliable way to know which you prefer … you can read a little more about the differences between how they feel in post #7 here.
You can read more about the different types of latex in post #6 here. Talalay comes in both a blended version (30% natural latex and 70% synthetic latex) and a 100% natural version. Dunlop also comes in either 100% natural or blended versions as well although the Dunlop that BB uses is 100% natural.
Almost all the latex you will encounter … either natural or synthetic … is Oeko-Tex certified.
Phoenix