SIGKILL vs cutting of power

What are differences for running program between sudden cutting of power and SIGKILL? We have microservices that use database. I am tasked with creating automatic test that simulates sudden power off (not nice shutdown but unplugging from power without UPS). Intent is that after powering back we want to verify that database is still consistent etc. I plan to simulate it using killall -9 microservice_name. How good is this simulation? Is doing one or the other more destructive? I am especially worried about flushing (or not) file buffers, but maybe there are other differences? Bonus question: what when we compare with not actual power, but sudden kill of virtual machine?