I've had both, and I preferred the gel. The sheepskin was fine in the winter for warmth, but for comfort, the gel worked much better. My old saddle was brick hard and that gel pad was the only way I could stand to ride while I saved up for a new saddle. (I had the sheepskin one first did have problems after a while with it stretching and then moving around on my saddle. Which was why I switched to the gel pad, and I was much happier with it.)
"Keep a leg on each side and your mind in the middle"