Do you think you get just as good of a work out using the treadmill as you do walking or running outside? Is one better than the other?

I think both are about equal.

I love walking outside.
As I walk my surroundings change and it certainly makes things more interesting.
I also climb hills as well as walk on flat surface.
I use to be the walking queen.

I like treadmills too.
Since this is an indoor activity the weather or season doesn't get in the way of that activity.
Where I live the summers are sizzling hot. So unless you get up really early it's way to hot to walk outside.
IN spring and fall we have a lot of pollen floating around. My car is often yellow in the spring.
Then there's the rain factor.

If I really had a choice in the matter I think I'd choose walking outside.
But
I don't really have much of a choice anymore.
Due to serious hip pain I walk on an indoor track.
Due to alergies and asthma indoors is best for me.

During my life I've exercised both indoors and outdoors.
I really think what's best depends on your own personal circumstances.
Afterall it's better to go with the exercise that best fits your needs
than
no exercise at all.

I find that I really enjoy walking outside much more than on the treadmill. Whenever I have the opportunity, I'll pick being outside. But you're right that it's good to have options for inside activity!