Stepper motors work best for high torque low-speed applications that do not require high power density. BLDC motors tend to work best at much higher speeds. Steppers are inexpensive due to their wide-scale use in CNC machines that have become popular in the maker and DIY communities. Steppers are generally smoother running but with FOC, there really isn’t much difference. Under FOC you could think of stepper motors as low Kv two-phase BLDC motors that are heavy for their performance.