Which is most effective during exercise: repetition or intensity? if i work out at a low intensity rate with a high number of repetition, will i get the same benefit as opposed to moderate to high intensity and fewer repetition? which matters most?

It is way better to mix it up & confuse the muscle then to keep repeating the same activities over & over. Otherwise, the body views the activity as simply being your normal routine & does not put much emphasis on enhancing the muscle being used. A varied exercise regimen is best. Remember also, muscles have 2 properties: power and endurance. Your routine should work toward improving both.