If you want to work "on" i.e. onboard planes you really need to be a technician or field type engineer.
If you just want to design & develop things around these then you can work on aircraft with an aerospace or electrical degree. Aircraft employ lots of complex avionics and on board computers & electrical systems.
The aerospace degree will focus more broadly on: aerodynamics, materials, structures/stress/dynamics, propulsion systems, thermodynamics (basically all the mechanical aspects of aircraft) as well as avionics and electrical systems.
But power electrical engineering will be much more focused, id imagine more depth on programming, power electronics, electrical systems... but to a greater range of applications.
its really a case of preference, what aspect of aircraft are you more drawn to.