When discussing voting, the point was made that there is a good side and a bad side to every ballot proposition. That is actually an exaggeration, as some ballot propositions are procedural and have no impact on individual liberty. Examples of this are California's 2010 propositions 20 and 27 which address redistricting, which the Libertarian Party of California has taken no position on.
Then there are complex measures, which have positive features and negative features. Those require more careful analysis, to determine whether the overall effect of the proposition is more beneficial than harmful. An example of that is Proposition 19, which has caused debate in libertarian circles.
Of course the purist argument is that "legalize it and tax it" contains three unnecessary words, that all that should be needed is "legalize it." In a perfect world a simple "legalize it" would be on the ballot, but the absence of a perfect proposition shouldn’t deter people from analyzing whether Proposition 19 is worth voting for.
So is Proposition 19 more beneficial than baleful?
According to Ballotpedia if Proposition 19 passes then the laws are greatly loosened. Persons over the age of 21 will be able to grow and possess small amounts of marijuana.
It does not address federal activities, and it is theoretically possible that local police could ignore this law by working with federal law enforcement. An unnoticed criticism of Proposition 19 is that, like 10th Amendment resolutions, it lacks teeth. Many police and district attorneys are against Proposition 19, and while they will be unable to directly act against small marijuana users they can always encourage cooperation with the DEA.
Overall though it is a step in the right direction. Not a full step, not a perfect step, but definitely in the right direction. Given how few steps there are in any good direction, this is definitely worth supporting.