When comparing a Struers diamond compound with other polishing compounds, I think the important point is not simply the brand. The diamond type, particle size, concentration, carrier, and polishing cloth all have a noticeable effect on the final surface.
For routine metallographic work, monocrystalline diamond is often a good choice when controlled cutting and a consistent finish are the priority. Polycrystalline diamond can be more useful when higher material removal is needed, particularly on harder or heterogeneous materials.
I’ve found that contamination between grit sizes can cause more problems than the compound itself, so keeping separate cloths and cleaning carefully between stages is critical.
For comparison, this Struers diamond compound resource covers both mono- and polycrystalline formulations.
What has given you better results in practice—monocrystalline or polycrystalline diamond for your harder metallographic samples?