Running on a treadmill, while it might not be "easier" in the sense of how much actual exertion you do (in fact, it might be harder because you can control speed/incline, is easier because you're indoors, in a relatively safe environment, as opposed to outdoors where there can be oppressive sunlight, cars, bugs, etc. There's usually air conditioning where a treadmill is, easier access to water/towels, etc.

I don't think running on a treadmill is any easier physically than running outside, it is more comfortable, for me anyway. I like to be able to watch tv and stuff; I've always preferred the gym.

I do know people that prefer to run outside though because of the "freedom", I've been told.

It is easier comfort wise, but yeah, running is running.

I personally think running outside is easier than a treadmill. You need good balance to remain on a treadmill in one spot for a while. Running outside is easier because you are moving and aren't just stuck in one spot.

When you use a treadmill, the tendency is you control your speed to avoid being left behind or to keep to the machine. When you run outside, your movement is free. No machine is keeping you from being slow or being fast in running. Plus, the fact that you have the chance to see the neighborhood, breathe fresh air(if your place is not polluted) and interact with people you may be passing by.

But sometimes, running outside takes a lot of effort than using a treadmill. If you are busy with other things like watching TV or you don't have a plan of going outside or it is raining outside, treadmill is better. You get to run inside your house.

It depends on what type of running is most applicable for a situation. Both are easy. You just have to choose which is most appropriate.

Running on a treadmill is slightly easier as there is no wind resistance. For example, if you are running 8mph outside you would need a fan or wind tunnel providing an 8mph wind on the treadmill to have an equivalent experience.

Some gurus estimate that this is worth about 30 seconds per mile. Your mileage may vary!

Whether something is easier is relative to your definition of easy. That being said, there are pros and cons to both.

Treadmill:
Pros - Inside, controlled climate, can do it while watching t.v., no dogs chasing you, no having to stop for red lights or traffic, no risk of being run over, no sharing your space with pedestrians or bikers, and easier on the joints than concrete or asphalt.

Cons - Slight incline built into most treadmills stresses the calf muscles more, balance is an issue because holding on while running doesn't give you the aerobic benefit that pumping your arms does, and breathing stale climate controlled air is not good for your lungs.

Outdoors:

Pros - fresh air, you control the speed more easily, and can stop more easily if needed.

Cons - Wind resistance makes running slightly harder, traffic signals and traffic break your stride and make it more dangerous, concrete and asphalt are harder on your joints, weather can keep you from running, animals can attack you when running, and you may have skateboarders or bikers who get in your way on sidewalks and refuse to move.

As a runner, I do find treadmills to generally be easier. It is not as fun though.
As far as the workout is concerned, runnung is running. The treadmill counts, especially if you utilize the hill and auto workout settings.I just think they are easier because you don't really have to watch were you are going and you can set the water right up there nice and handy.
Although, not that I have a Camelbak hydration pacI can run on the street with hands free and no worries.
The legs do not know what surface they are on just that they are moving. Get out there!

Running on a treadmill is easier because you have different settings that you can control on a treadmill. Running outside depends on the temperature, humidity, and weather conditions. I do both, but I use the treadmill more because of its easy access. You can do it at home and fall out later when you are done. Haha

Yes, treadmill work is considerably easier. To make it simple, there is much less involvement from the hamstrings (back oof the leg) and gluteus maximus/minimus (butt). The reason is a lack of forward drive. The treadmill's belt is constantly moving, so the "ground" underneath is taking the place of you drive.
While inclining the treadmill will help, it's still not nearly the same. But yes, it is still running, lacking the aforementioned points.
Many people will chime oin to tell you that the elliptical trainer is so much better. While it iis a good machine, real studies have not shown it to drastically improve the volume of muscle work load. This is a common misconception.
Running on a modern treadmill presents much less impact on the joints and feet, though. Those with shin splints may find a slightly inclined treadmill more comfortable.
It's also important to understand the different training volume and intensity level differences. There's aerobic (cellular respiration in the presence of oxygen-better for fat reduction) and anaerobic(oxygen deprived cellular respiration-more like athletic conditioning).