Hi Sander,
By size reduction, I assume you are referring to the size of the hollow-sleeve when comparing the Sigma models to the Alpha NR's outer tubes. Caelin continually research's and designs to improve not only performance, but also to improve the flexibility and ease of use of the power cords. The Alpha NR is the latest example of an advance in this area. The Sigma NR models are also more flexible and easy to bend than the previous Sigma models. There is also a Sigma EF now, which uses a smaller tube and is made to be as flexible as possible for a 6 gauge aggregate conductor set. The goal is not large and stiff; instead we aim for easy to use, light-weight and flexible.
Although Alpha NR uses an 8 gauge conductor-set, the it is lighter in weight and more flexible than the previous Sigma models. In part, that was accomplished by using the more narrow hollow-core tube that contains the conductors, along with changes in insulation and how the conductors are aligned within the tubes. I would not say the Alpha NR is superior to the previous Sigma models. I would say they are comparable to the older Sigma models, which is a real accomplishment given the Sigmas were $1,000 more in retail price.
Thanks, Sander. I hope this helps.
Grant