ELF's Studio Fan Brush, the 925 Brush is half the thickness, a third as dense, slightly less pliable, and about 2/3 as wide as ELF's fan brush. Bdellium Tools' fan brush washes well, the green dye doesn't bleed, and neither type of bristle seems to stain. There's nary a hair out of place and shedding is a non-issue. The 925 brush dries extremely fast.
As a rule of thumb, fan brushes are extremely multi-functional. That's true for the 925 Green Bambu Duet Fiber Fan Brush, but I feel like it's feathery construction makes this brush better for some uses than others. My favorite use for this fan brush is blending liquid highlighter and applying powder highlight. I also use this brush to very lightly apply loose setting powder. Bdellium's 926 Brush is a little too flimsy to accurately apply blush, bronzer, or contour. Bdellium Tools says their 925 Fan Brush can be used to brush away fallout, but I don't find it effective for that purpose.