What are the pros/cons of ram air turbines? Commercial aircraft are equipped with ram air turbines that can be deploy to provide power in case all other sources of power are lost. Ram air turbines have the benefit of providing power as long as the aircraft is moving through the air. However, aircraft are almost always designed with internal generators, driven off of the engines.

There is a limited case of adding generators to older aircraft. But they are also used to power large accessories, like the jamming pods on the EA-18 Growler. The EA-6B, which the Growler replaced, was also a modified attack aircraft using jamming pods with ram air turbines. Larger aircraft that are modified for the electronic warfare role don't seem to go this route though.

Obviously the turbine will add drag, and it seems like internal generators are more efficient, since almost all aircraft are designed to generate power that way.

So my question is: what are the benefits or drawbacks of using ram air turbines to generate power? While they are generally saved for emergencies, what makes them more useful in cases like jamming pods, compared to other options?
You have kind of answered your own question. The down side to ram air turbines is they cause drag.

The up side is that they provide power outside the internal generating capacity of the aircraft (e.g., in emergencies when there is no power).

In the case a of a jamming pod, having its own power source eliminates/reduces the need to rely on internal power. That makes the pod modular. If the pod did not generate its own power, there would need to be a generator inside that sits there regardless of whether the pod were attached.