These terms are not mutually exclusive or in my opinion, all that necessary. I believe all energy we use for spirit communication, healing, etc. is channeled from source. There is only ONE source. We as humans feel the need to "identify" an energetic, spiritual counterpart in the channeling process. So we assign terms like angels and spirits and guides.
The term "Angels" is generally embraced by those who have difficulty detaching from organized religion due to fear, guilt,