Deleting the cache makes only sense if you realized that the imported targets are not good or wrong.
Deleting history is a good choice once you decide to try to submit to any targets from the past as e.g. your filters changed, new engines have been selected or e.g. you added a better captcha solution.
Comments
cache = imported urls, found urls that have not been posted to
history = urls the project posted/visited before and will not tough again.
Deleting the cache makes only sense if you realized that the imported targets are not good or wrong.
Deleting history is a good choice once you decide to try to submit to any targets from the past as e.g. your filters changed, new engines have been selected or e.g. you added a better captcha solution.