since i'm dieting down and my goal is to burn as much as possible. I'm doing cardio 3-4 times a week first thing in the morning. I like to switch it up if i can. I usually do stair master, bike, elliptical or walk on a treadmill at a high incline. I tend to do about 30-40 min of cardio. Sometimes i get bored at the 15-20 min mark and switch to something else. I don't think there is only one type of cardio that will help shed the fat the fastest, i just try to keep my heart rate up in order to burn as many calories as possible.
by the way, i really hate cardio. it sucks on a keto diet