We ship USPS Priority or UPS Ground depending on what is faster/cheaper on a package-by-package basis.
SE should be able to take the package dimensions and weight and show the rates for both carriers side by side by default so I don't have to refresh the page each time (and reselect shipping speeds). Then I also wouldn't have to keep remembering what the other rate was for comparison.
Ideally, users could set their default shipping methods (2 or more) and SE would just show a table with the rates side-by-side with purchase buttons next to each other.
Would save me HOURS.