To calculate power consumption for three phase:
P=3^?* E * I * cos theta, usually p.f.=0.8
use the highest amp reading for variable "E".
this will allow you to determine the cost benefit of operating in 380V or 660V. there are other factors to which to consider such as power source, ie. transformers necessary, application, and maintenance factor, etc. which can drive up your cost.

The voltage used will depend on the HP you need to perform the work.
Using Delta or a wye connection will depend on the motor application whether its for speed or torque applications.
There are many Wye-delta switching motor starters to consider.