A weekly PCR test has only a 60% chance of identifying COVID while someone is infectious. This rises to 85% when done every 3 days. Daily antigen testing is far more practical than either and achieves 90%. https://x.com/DavidJuncker/status/1411070440836055044

Yes, PCR is better at detecting the virus before contagiousness, but not incredibly so: 70% the day before vs 40% for antigen. Once again, if your goal is to prevent spread, frequency and turnaround time of testing matters MUCH more than analytical sensitivity.