Should I default to pull-up or pull-down resistor with tact switches?
Some times you can gain a reduction in current by choosing one over the other.
For a momentary switch this would not be the case.

If all other things are equal I would favor a pull-up resistor. Some microcontrollers (like the Atmega series) have inputs that can be configured with an internal pull-up. 
Using only pull-ups (internal or external) does provide some consistency.