Whole muscles are far superior to trim. This has to do with the microbiological properties of trim, which directly relates to its flavour when eaten. The far greater surface area of trim compared to a whole muscle leads to significantly more temperature rise, and hence oxidation (which is essentially the deterioration of preferable flavour producing compounds into objectionable ones). Additionally, there is more surface area for bacteria to infiltrate. The interior of a muscle is sterile, but the outside can be potentially contaminated. With this in mind, picture the surface area of a box of tic tacs versus those tic tacs within the box scattered on a flat surface. Hence whole muscles are very much preferable to trim for both the safety of the final product, and directly correlating to this fact, imparting the taste we commonly associated with the freshest, best quality beef.