Going outside is always better, but when you cannot, it is good to have a treadmill. I think if you are comfortable on a manual one, get it. It is better exercise, and you can burn more calories that way. Helps to maintain a healthier lifestyle if you do not miss workouts b/c of weather. Just make sure you stay hydrated, b/c you can sweat a good amount indoors. Plain water as well as other diet drinks.
I am my own Keeper