I agree- 1969 S would be higher AU than the '64. Don't send the coins to get graded though, it wouldn't be worth it.
They're both about the same. You can't compare detail on a 1964 with a 1969. They reworked the hub in 1969 to bring back a lot of detail that had been lost since 1918. The IGWT lettering was also reworked.