The elliptical trainer has the advantage of working the upper body more. But let’s make a match between these 2 cardio machines according to your goals:
If your goal is to lose weight, I’d say it’s a draw. At equal intensity, you will lose about the same number of calories for 1 hour of exercise, whatever your choice.
To build muscle, I would give a small lead to the elliptical for the fact that it works the upper limbs slightly. For the buttocks, the elliptical trainer is also in front. Nevertheless, don’t kid yourself, it’s not with a cardio training machine that you’ll really build muscle.
For fitness, I would again give the advantage to the elliptical because it is less constraining for the knee joints (you will perform circular movements). Even if running on carpet reduces the shock compared to running outdoors, it is still not recommended for those with joint problems.
Verdict: The elliptical trainer is a bit ahead in performance, but it is also more bulky (you can find treadmills that take up very little space when folded). No problem if you do it in the gym, but a point to consider for home use. But best of all, it’s still what you like! If you enjoy training on a treadmill more, then it is the one you should choose.