Contract Bridge Games Verses Party Bridge Scoring?
Neither - as each hand is scored individually for the Game Bonus of 300 Non Vulnerable and 500 Vulnerable. 

One option that I have seen played is to carry part-scores forward after any of the first three deals of a set instead of awarding a Part Score Bonus of 50. When this is done the Part Score Bonus is 100 rather than 50 on the Fourth hand, when the set is closed off. Be sure to discuss in advance with your partner and opponents if this option is in effect.