I prefer the two pocket ones myself, particularly the one made by Black Widow. However, there are certain bows a two pocket stringer doesn't work very well on. Some bows have tiny upper limb tips, and the upper pocket swallows up the string groove. They don't work well with some longbows because the upper limb tip tends to slip out of the upper pocket.
For those bows, a stringer with a rubber pad works best. Use one that is new enough that the rubber is still soft and will stick easily to the limb. As was mentioned, using two feet on the string gives you better leverage on the upper limb, and will make it easier to get enough bend in the limb to string it.