The official summary suspiciously gets this one wrong. Prop 93 does not reduce term limits. Prop 93 changes term limit. Only in a narrow sense does prop 93 reduce term limits. In general, prop 93 lengthens term limits - as is portrayed in most pro-93 ads.
Under current law, State Assembly Members can serve a total of 6 years, and State Senators may serve a total of 8 years, for a combination of 14 years. But because there are double the number of Assembly Members as there are Senators, at least half of the assembly will not go on to serve in the senate. For these people, 6 years is all they get. A limit of 12 years in either house will double the term limits of Assembly Members and add another term to State Senator's terms.
While in theory more experienced politicians are better than less experienced politicians this doesn't work out in practice. Politicians work hard - at maintaining their offices that is. That's why something like 95% of incumbents win elections. California, and most other states, have been redistricted in order to make districts sure-wins for their party. What decent self-serving politicians wouldn't vote for redistricting when it guarantees them a win?
Prop 93 doesn't necessarily help Californians. Politicians will just have longer to sell themselves to corporations while not having to worry about actually working for Californians, as long as they do the bare minimum.
I want to see a system where politicians have to work hard for the constituents because they could legitimately lose elections. That's why this is such a shame that the 2006 initiative which would have set up independent judges to redistrict California didn't pass. Term limits will at least mandate that we get fresh blood into the offices every so often.
On the other hand, good politicians will have less time to build connections and gain experience.
Because there is a mix of potential benefits and cost, I don't have strong feelings about a yes or no vote on this proposition, but I'm recommending we vote no. If we ever outlaw gerrymandering, I would vote yes.