At the gym, I use a Precor efx556i and at home and office, I have a KeysFitness (that I got at Playitagainsports.com) Cardiomax 705 http://www.keysfitness.com/el-cm705el.html
. I can use it at noon or after work on days when I know the gym is going to be busy...like right after Jan 1 with new year's resolutions and right before Summer with those who are going to lose 80 pounds so they will look good at the lake, lol.
I like the ellipiticals better than treadmills for four reasons:
1-you can go forward or in reverse. Turn up the resistance and your stride count and go as far as you can. Then stop and go in reverse. Different muscles are worked in the opposite direction that a treadmill does not hit. It is like doing regular bicep curls and when fatigued, you can still do hammer curls as your brachioradialis is not fatigued.
2-you can turn up the resistance and increase your leg strength and endurance.
3-you work your arms, shoulders, back and chest, whereas the treadmill does not require this activity. You get more muscle groups recruited and burn more calories.
4-you do not have the impact, as noted above, upon your joints. The motion is more like treading water as it is smooth and uses more muscles.
If you have a TV close by, that helps a great deal, too. You can have a ralatively controlled climate with your elliptical indoors that you do not get with running or cycling outdoors. I hate to ride in a crosswind.
Good luck on your workout.