New Building VS Expansion

I recently built a passenger terminal in my hub. To give it what I wanted, it cost about 2.7 million, and it handles 2000 passengers.

The question is, when it comes to needing more passenger handling, is it better to buy/build another terminal for the 2.7 million, or expand to 4000 passengers at a cost of over 3.1 million? Is there any bonuses for continuing to use the same terminal, or drawbacks for having more than one terminal at an airport?

I did notice a very small increase in the number of employees (like, maybe 10 at most) when the building was built and put into operation. That would probably happen with each building, but would also happen with expansion. More PAX = More Staff.

Any help is appreciated.

Expanding your terminal would make much more sens IMHO. Since it could potentially cost less, and either way, it uses the same amount of space as 2 buildings.