Representatives vs. Senators. Difference?

They are the main forces in the Check and Balance game within the two house chambers...If the Republicans will dominate the Upper House (Senate) then chances are very slim for Democrat Reps to further any bills at any occasion...On the other hand, they both hold "Power-Sharing" authorities as well, and this would become one of the best if not the worst check and balance as well as power-sharing scenarios that could happen in the near future if the two chambers are that divided...