Whats the top notch product to use to run water lines?..copper, kyteck, etc....? want it to last, and work!?

doing some home reno'z, and I want to increase the pressure from my hot water take to most areas (mainly Bathroom). Also, building kitchen sink and need to run all new line. Just wondering if I should stick to copper, as everything else is already copper.....if it would be cheaper to use the new plastic material on the market. Copper is obviously more $$$, but is it really the best bang for the buck?