I think what you're talking about is stability, and again it depends on what you mean by stability. Policy lurches that occur in a first-past-the-post system would not occur, or are less likely to occur, in PR systems. PR systems, if they are more centrist and govern for a longer period of time, are more likely to have that same kind of longer-term stability.
On July 28th, 2016. See this statement in context.