Generally speaking, use 3 phase whenever it is available. For the cost of one additional conductor, you increase the capacity of the panel by a factor of 1.73(over single phase).
But, if you consider the cost of the minimum size allowable panel (often 100 amps) versus the cost of a 3 phase 100 amp panel, AND, if the total load to be used can be handled by the single phase 100 amp panel, then that is the most economical choice. (As is the case in residential services.)
In your case, the industrial load may not be sufficient to warrant the additional cost. The question you need to ask is: Who is paying the bills, and do we want to plan for any future loads?
