In reply to Cathcart_Alpinist: Actually it's the opposite. It's the nylon in dyneema slings that fluffs up, not the dyneema. Dyneema is very very abrasion resistant but not very CUT resistant, hence they are banded at the edge with nylon to prevent cutting. The dyneema is the white part of the sling - if you inspect an old sling, you'll find it's the coloured bits that are fluffy.
Are nylon more resitant? Maybe but I'd have thought mainly because they are usually much fatter than dyneema ones... seeing as you should be replacing your slings every few years anyway is it even an issue?