The BLB lamp is basically the same as the BL lamp except for the filtering elements in the glass tube. The tube filters out light (energy) that is visible to humans. My experience leads me to believe retaining this light (using BL, not BLB) increases insect response. Tests with houseflies tell me exactly that.
We have and will sell BLB lamps. We don't recommend them. We will try to talk you out of it. We don't believe there is any reason to use a BLB lamp except perhaps for decorative purposes. BLB lamps cost more and give you less fly attraction.