A quick jaunt to wikipedia...
"Jived fox nymph grabs quick waltz." (28 letters)
Short, but nearly incomprehensible. 2/10.
"Glib jocks quiz nymph to vex dwarf." (28 letters)
Just as short as previous, but contains glib jocks and a vexed dwarf. Superior. 6/10.
"Sphinx of black quartz, judge my vow." (29 letters)
One letter longer, but rad as fuck. 9/10.
"How vexingly quick daft zebras jump!" (30 letters)
Sentence reads in my head as British accent, contains the word "daft", and "zebras." Solid. 7/10.
"The five boxing wizards jump quickly." (31 letters)
Starting to get longer and therefore points deducted, but easy to remember, sounds normal, and contains boxing wizards. 6/10.
"Pack my box with five dozen liquor jugs." (32 letters)
The longest, but also the most likely to actually be said out loud in real life. 8/10.
Result: Sphinx wins, but Liquor jugs is a close second. If British, Daft Zebras best.