I prefer Ultracam strings, because they have the least stretch to them, in my experience. I've made about 50 of these strings and haven't seen one break yet. Many have 10s of thousands of shots on them. The real key to getting a good string is to find the best stringmaker. The brand of string material, will be a secondary consideration. A good stringmaker will keep creep to a minimum and can prevent serving separation with proper string making. My own recomendation is to pay no attention to which is claimed to be fastest. Speed can be obtained with many string making techniques, like smaller diameter servings or fewer strands in the string. In the end, we're only talking about a few fps, and sometimes this is gained by paying a price in durability, noise level and ability to resist creep. In my opinion, the most important task of a stringmaker should be to get the most stable product possible.