Though if you include the dash to use those as flags, the second one is wrong (it treats the "v" as the file name for "f"). Without the dash, the next positional argument is the file name.

Examples: These do the same thing:

  tar cfv foo.tar a b c
  tar cvf foo.tar a b c
  tar -cvf foo.tar a b c

This errors, trying to add foo.tar to archive v:

  tar -cfv foo.tar a b c