I ran track in high school and college. Believe me the same arguments concerning intensity vs volume exists somewhat in the cardio world. If you're concerned with the health benefits of cardio exercise like making your heart muscle stronger that is illustrated by the lowering of your resting heart rate, decreasing visceral fat and subcutaneous fat, increasing red blood cells; lowering blood pressure; lowering of blood sugar; lowering of blood fat as in triglycerides; changing the ratios of hdl's and ldl's in your favor; and other benefits like increasing your gas tank so you don't gas there are many ways to accomplish this.
Since your using cardio as a supplement to bodybuilding it doesn't have to be complicated. Using high intensity or low intensity it will get you there. If you have a specific athletic attributes you are going for that changes everything in how you approach it. In general unlike strength training you improve cardio capacity by frequency. Meaning 4 days is better than 3 and 5 days in general is better than 4. Look to get at least 20 to 30 minutes at minimum a session. I prefer running. It's the gold standard that all other cardio is compared to.
If you want some specific recommendations write me.
