Fabrell's are fun, though abit more costly that prismas over here. But can be worth it when colored with the right way. I like prismas, there pretty smooth, but I don't use a colorless blender. <.>
I think you can get the smoothness with practice on any type of colored pencils. I did this without my white colored pencils( that's what I use to help blend)
Artz
though, mixing fabrell and prismas is what I used to do long ago. I sill use my fabrells for certail colors.