We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
As our readers know, we view what most people term "cardio" as about 1/3 of the general fitness triad (resistance, calisthenics, and cardio).
Among the machine options, the rower and the stair machines are most designed to help build some strength along with the heart stress. The advantage of the rower is that it is pretty much total body, and when you up the resistance, it's some strength along with the cardio.
To beat a dead horse, cardio is meant to be about heart fitness, so if your heart rate is not where you want it then all it is about is physical endurance (which is not a bad thing in itself).
The Maggie's protocol advises sprints for cardiac fitness, not long-slow. Long-slow, like walking or swimming laps, is fine for ordinary endurance and maintenance. It all depends on one's goals.
I like mixing up my cardio days with variety to avoid boredom. Treadmill sprints, rower, stair machine, ski machine. Usually only 30 minutes, then I finish my hour with accessory weights.
Reminder for January fitness people: unless you are a unicorn, do not use exercise to lose weight. That's not what it is for, and it only works for the rare unicorn. Exercise can be good for muscle weight gain, though, especially weight training. Losing fat is about nutrition.
I like pushing the prowler sled. Its scalability of effort is one of its great advantages. Sprint, jog, or walk, load it up with a bunch of plates or keep it light. No eccentric loading so easy to recover from with little to no soreness. No real technique to learn like with a rower (which is fun to do, though) and no chance of falling off like a stair machine or treadmill. Also, when it's loaded up heavy, you can build some strength, which you can't on the stair machine or rower, despite Dr. Bliss' statement.
When doing cardio intervals on a machine, I find a rower or a stationary bike much easier than a treadmill; its much easier to handle the acceleration and deceleration. I also find its way easier to do intervals on a rower than a longer steady effort, as my rear gets sore; i've found 6 -8 times 3 minutes hard then walking around for 2 minutes works perfectly.
Still, as i've remarked on here many times, the best workout program is the one you'll actually do consistently, so pick the one you enjoy doing over trying to find the "best"