A good shipping supplier overview (Sept 1, 2021) https://fitsmallbusiness.com/fedex-vs-ups-vs-usps/
This year FedEx On-Time performance suffered because it has been transitioning away from SmartPost and moves away from USPS. In March FedEx announced that their SmartPost business was being rebranded as FedEx Economy and that last mile delivery operations formerly handled by the USPS has now been fully integrated into their Ground network. This change marked a shift in FedEx strategy as it made themselves more competitive by moving to 7 days/week delivery. But in the short-term, they suffered a drop in On-Time deliveries which is now starting to get better.