Treadmill or Elliptical

I unfortunately live in an area with extremely bi-polar weather. I dont plan to purchase either of the above , treadmill or elliptical but where I work has both in the training room but that is all they have. I use both but I feel like the elliptical does more for me. I will look into the items to help moitor my heart rate; I dont feel bad when it gets that high, 200 or over, it just makes me nervous.