I hear people talk about how the long-tail CO is stretchier, but I just don't like it! Mine stretches, but not enough to where I want to use it for socks.
Instead, I use the overhand CO where you loop the yarn around your index and middle fingers, slip the needle under it then slip the yarn off your fingers and onto the needle. It's not as strong and to get the maximum stretch, you have to space the stitches quite a ways apart. This makes working that first row a real pain, but I've always been happy with the results! If I have too much trouble getting the spacing between the stitches right, I will change to needles 2 sizes larger and do both the CO and the first row. I tried this same trick with the long-tail CO, but it didn't seem to make much difference!