i have both a pair of zensah calf sleeves and some c.e.p. socks. frankly, both are better than nothing but between the two, the cep's are far superior. first, they're a medical grade compression (medi) and the compression is graduated below the calf and then consistent around the calf to help increase veinous return. i use them mostly post workout/long run and can definitely notice a difference...even for my sore achillies which i've always had issues with. they're a little more expensive but worth it.
for what it's worth, i don't work for either company but do work in a running specialty store