
I'm trying to quickly build up a solid base of the first three and wondering what the most efficient method is between upgrading (3 rooms) and building (3 rooms).

The main reason I'm wondering is that in my vault I'm going for 3 layers of the following (power, food, water), followed by several layers of med/rad labs for mass-storage purposes, training rooms, etc. I am trying to figure out what will get the best return on investment right away. I am wondering which is more efficient in the beginning: building new rooms (production specifically) or upgrading existing rooms? Assume that the rooms are already three wide and that I would (obviously) be upgrading them all at the same time.
