Final answer:
White dwarfs are more common in our galaxy than stellar-mass black holes because most stars are low-mass and will become white dwarfs rather than evolve into black holes.
Step-by-step explanation:
The answer to which is more common in our galaxy, white dwarfs or stellar mass black holes, is white dwarfs. Stars with masses of 8 Msun or less, which constitute the majority of stars, lose enough mass through their evolution to become white dwarfs, each with a mass less than the Chandrasekhar limit of about 1.4 Msun. On the other hand, stellar mass black holes are produced by the core-collapse supernovae of much more massive stars, which are less common. Therefore, white dwarfs are more prevalent in our galaxy because low-mass stars are more abundant and most will end their lives as white dwarfs rather than evolving into stellar mass black holes.