I'm not sure what the translucent material is either but WC uses mostly BCY 8125 (95%) and some 452x (5%) for their strings/cables.
I had some bad experiences with 100% Vectran failures so I am untrusting of materials with a high Vectran makeup. You can pull on Vectran forever and it won't break, but it weakens and fails quickly at sharp bending points. I prefer 452x over everything else and it has less % of Vectran than the Ultracam. Adding more Vectran than is needed to stabilize the material just slows the material down more than necessary and makes it less durable IMO...
The following was copied from the WC web site:
Q- What is the difference between 8125 and 452 materials? How about D-75 thin and Ultra Cam?
A- Right from the manufacturer the BCY 8125 material has more inherent movement the BCY 452. However, with our construction process we can remove almost all the movement in the 8125 material in most cases. This makes both materials very comparable in terms of stability, however some shooters, particularly in the target archery sector, feel that the 452 (which is 450+ in half sized strands) are slightly more stable. About 95% of our customers are using the 8125 material and experiencing great success. D-75 thin is a Brownell material that has basically all the same attributes as 8125. Ultra Cam Is a blended material using Dyneema and Vectran fibers ( as is 452). The major difference hear is that Ultra Cam has a higher Vectran content than 452. In Non-prestreched strings higher Vectran content can help to maintain stability, however Vectran is a more brittle material, and may be more prone to speed loss, vibration, and usually has a shorter useful life than 100% Dyneema materials like 8125 and D-75 Thin. All of these materials are excellent choices for today's compound bows. We recommend you take into account your own preference and shooting style when making your final ordering decision