Hi poloramos,
Welcome to the mattress forum:).
Is cooler the only benefit you are looking for? What kind of mattress are you putting the wool or Talalay topper on? There is not really any data on comparing one material versus another and how your body retains heat. Too many other factors to consider also.
There is more information about wool toppers and how they compare to various foam toppers (at least in very general terms) in post #8 here and in posts #3 and #6 here and there are some additional comments about wool toppers and a list of some of the better sources I’m aware of in post #3 here.
While it’s not always possible to track down temperature regulation issues for any particular person on a specific mattress because there are so many variables involved (including your room temperature and humidity, your sheets and bedding and bedclothes, your mattress protector or any mattress pads you are using, and where you are in the “oven to iceberg” range) and some people can sleep warmer on mattresses that most people are generally fine with … there is more about tracking down a potential cause or causes for temperature regulation issues (at least to the degree possible for a specific mattress) in post #2 here and the posts it links to that may be helpful (including more information about the wool fleece toppers vs toppers that use wool batting).
Thanks and let us know if you have other questions.
Sensei