I prefer Damier. It is more discreet, not as widely carried or widely knocked off, and is actually the oldest of the LV patterns (was created by Vuitton himself in 1888; the Mono Canvas didn't show up until a decade or so later, after LV died.)
Edited to add: Also, it is more practical (the vachetta on the Mono Canvas does get very dirty after a time.)
Ash