Output transistor Re selection

I understand the how's and why's of setting the quiescent current for output transistors for a given emitter resistor value. What I would like to know is how to choose the value of that resistor. I see amps with as little as .1 and as much as .5 ohms around here. That's a 500% spread, so there must be some logic as to why a particular value is chosen.

My guess is that you want it low enough so that you are reasonably close to unity gain, but high enough that there is some emitter degeneration/thermal stability built in. That being said, how are the actual values determined? I realize there probably is not a single answer to this, but I at least want to know the thinking that goes into it.