I cant say I have done any studies but as of two winters ago the fleece on seemed to cool a bit faster. The last wool one we had just seemed to hold the moisture and not wick it off the horse as fast. To be fair, it was old and probably could have used a cleaning.

For us the fleece works well, is cheaper to buy and easier to clean. We use them a lot in the trailer since they are easy to use when traveling. We have taken to buying them in June/July when they have them for sale at $39.95. At that price I dont cringe when I see them rubbing against a stall wall or fence while they cool off.

Regards,
Mark