I tried both ways... I like it better with filter sock. I change it every 3 days. bought 10 of them and wash once a month..
without filter socks, my sump got dirty really fast, a lot more sump cleaning.. nitrate shot up a little too because I kept water changes the same. I over feed my LPS tank and run the water dirty.. socks really help maintain nitrate if you remove it fast enough
no major impact on skimming, except new socks drives skimmer crazy for the first hour..