That's a really good question.
You'll probably get more inherent cut from the thin foamed wool pad.
Microfiber's advantage is the ability to hold more abrasives - increased surface area. The fiber itself is relatively gentle. Wool fibers on the other hand are thicker, and naturally more aggressive. Both pads lack a thick foam backing, which transfers the backing plate energy directly to the fibers.
I've used the thin foamed wool, but not the xtra cut though, so take it with a grain of salt.
The thin foamed wool was monstrous in defect removal, but a very uncomfortable user experience.