UPS Mail Innovations beats out USPS First Class for us in price and accountability. Because they push through UPS's system all the way to regional facilities, we're seeing less package claims.
UPS SurePost also can be competitive if you put them through the wringer. From 1-9lbs we're saving between $0.08 to over $22.00 across the Contiguous US.
USPS almost retained our business from 10-15lbs, but we got UPS to match them.
Their price point can't be beat for < 3 lb items domestically.