I won't be of much help with those particular pants, but will say that in general polarplus/fleece/synchilla/etc make GREAT durable garments. The biggest problem is that they can often be too warm. It will depend a lot on your metabolism and how you'll use them. I tend to favor cold and when doing strenuous activity will shed layers. I have a umber of tops, bottoms, jackets, etc in fleece and the ONLY downside I see is that fleece can be bulky. It performs well even wet...just shake or spin the wet garment around and use centrifugal force to push water out of the garment.

BTW, you might try Sierra Trading Post and even ebay for markdowns or cheaper offerings if the cost is of concern.