I think these are two very different areas and it really depends on what your goal is for the future (and what you like to do). My Air Force experience is quite diverse and I have worked in both areas. I have been an aircraft maintenance manager and I have worked on jet propulsion projects. There is huge job scope in both areas, although aircraft maintenance is much more specific to that area.
From a propulsion perspective, the study could lead to roles in new technology, research and design or in a more managerial role for engine development and capability.
From an aircraft maintenance perspective, you're managing maintenance resource and procedure. Understanding implications of maintenance on aircraft, identifying risks, improving procedures, looking at alternative ways to achieve a task. There is a lot of problem solving required and working with / bringing together your team to achieve this.
Catherine recommends the following next steps:
- Understand what you like to do, this may change as you study further and as your career develops, but its a good start to motivate you.
- I think it would be good to understand if you're highly technical and want to be the designer, or if you're looking for something slightly more general in a managerial role - an ability to delve into the technical and bring together the tech specialists to lead them towards the goal.
- I would also try to speak to a number of individuals who specialized in propulsion to understand more options for the future before you make the decision.