So the SBD is made of BCY-D10 as opposed to Champion's with BCY-X.
I (Champion Custom Bowstrings) offer several materials, but BCY-X is my current favorite.
I haven't heard the BCY-D10 discussed (I think?) How does that compare to the BCY-X?
Dynaflight '10 is 100% SK78 Dyneema. BCY-X is 83% SK90 Dyneema and 17% Vectran. The higher grade Dyneema means less stretch/creep, and higher durability. Vectran further stabilizes the material, especially in higher temps, and seems to make the material quieter.
Also, I believe these are all 'skinny' strings correct? Are they all the same size??
Depends on what you call "skinny". I like 18-20 strands of BCY-X, which equates to about the same diameter as 10-12 strands of Dynaflight '97. Dynaflight 10 is a larger diameter strand than '97.
I can use fewer strands in X, but I don't recommend it. In around 20 years of making strings (making well over 10,000 strings) I've found no real benefits to very small diameter strings, but they are going to be less durable with more stretch/creep. My experience--yours may vary.