Efficiency conversations usually start at the wrong end. By the time a project is comparing chiller COPs, the decisions that determine most of its energy consumption have already been made: orientation, glazing ratio, shading, insulation and the assumed occupancy profile.
The load is the design
A mechanical system can only be as efficient as the load allows. Reducing peak cooling demand through envelope and orientation decisions shrinks the plant, the distribution and the electrical infrastructure behind it simultaneously. Equipment selection then optimises what remains rather than compensating for what was avoidable.
Part load is where systems live
Plant runs at design condition for a small fraction of the year. A system selected on peak efficiency alone frequently underperforms a lower-rated system with better part-load behaviour and a control strategy written for it. Modelling the annual profile, not the peak hour, is what separates the two.
What this means in practice
Bring the mechanical engineer into concept design, not into documentation. The cost of that involvement is trivial against the operating expenditure it influences for the following twenty-five years.