Good point. If we rank the use of different gold nanomaterials by size and shape for use in an assay from least sensitive or effective to better performance here is how I would rate them

Rough gold nanoparticles - different sizes and shapes - lack of uniformity

Gold nanorods - superior lumenescence to gold nanoparticles due to uniform tubular shape. Commonly used in assays but lack some advantages of the next two materials -

Gold nanocrystals - uniform ordered shape and size for surface functionalization and lumenescence advantages.

Gold quantum dots - distinct advantages of quantum confinement for tunable broad excitation and narrow emission spectra, signal brightness, high quantum yield and photo-stability.