This is a new system so your pump arrangement and piping arrangement and the potential use for VSD's on the pumps can have a huge impact on your plants efficiency. You could have several small chillers in decoupled loops, each with it's own chilled water pump. With modern automation there is so much that can be done to make aplant efficient. Your focus shoud be total plant efficiency, the whoe plant not one component of it.
I would suggest you get a professional engineer or at least search the ASHRAE website as well as the department of energy website for chiller plant design tools. Your leaving a ton of money on the table focusing on chiller manufacturers sales data.