If you are doing Bonnie Hunter mystery quilts I recommend that you get strip dies (which you can also use to subcut squares and rectangles and diamonds) and since her blocks tend to have many smaller units, if you are doing her 12" blocks you really would need to use an 8 or 6" Qube.
I only buy Blocks on Board (BOBs) that I know I can use several ways--like the log cabin die, or ones that I need because it has curves that I'd be sloppy with , like the 6" DP or the Cleopatra's fan.
I also am doing a RuthAnn Barry 3D quilt and needed to cut 625+ equilateral triangles--so bought the die! Would never get it done with out that die and even though more scrap than if I'd bought a new ruler it is so worth it--especially as all 3 grandsons will eventually get one of these!