Honestly, I'm not huge on the fluff as of yet. I guess BA fluff is okay, in comparison.
I don't really care about the colour scheme. It may get me in trouble, but I don't like painting according to the scheme anyway. What is the point of painting your own army if it is just going to be exactly like every other army??
I chose BA because of the wings!!! Spacemarines with wings! I only just bought my first 40k army the other day. Dante and a squad o Sanginary Guard and a pack o Death Squad. Sanguinor is in the mail. As much as I can I want to focus around a core of Sanguinary Guard units because... WINGS!!!
