Look for machines with programs that allow you to adjust routines based on your fitness level and have heart-rate-controlled workouts that consider your age, weight, and gender.
A good display will have easy-to-use controls and will show some combination of your heart rate, calories burned, speed, resistance levels, and details such as time and distance.
Gadgets, such as MP3 docks with speakers or a headphone jack, or LCD TVS, don't have much effect on performance. But if they entice you onto the elliptical, they might be worth your while. Newer features, such as USB workout trackers or virtual trainers, might inspire you to intensify your workout. Some users might find the lack of a magazine rack or water-bottle holder to be a nuisance.
Those with a chest-strap heart-rate monitor are best because they don't impede your movement. Contact monitors measure your heart rate only when you're holding onto them, which can impede your natural stride. But it doesn't need to be a deal-breaker; stand-alone heart-rate monitors are available for about $35 to $110.
You'll also want a machine that is easy to adjust and has a variety of workout levels. Look for an elliptical exerciser that has a range of resistance that fits your workout needs.