They are very similar. The Ultracam has a slightly higher percentage of Vectran. Vectran will not stretch - even a little, but it is more brittle. In theory, Ultracam would be more stable, and more likely to break. In reality, I don't think the average person will notice a difference between the two in actual use. I've made many Ultracam strings and have been totally satisfied with them. I'm sure you can get many string makers to say the same about 452.