people say its the oppositte, that running outside is harder and your 1.5m time is more realistic (which of course it is) but yeah I find it harder to run indoors, the monotony and the temperature affect me.
Physically the treadmill is easier for a number of reasons, but the mentality of it will affect you a large amount; if you like some scenery, or actually watching the distance decrease then you may find yourself a lot faster outdoors.
Treadmills are definetkly boring, in the end you're staring at the wall/window for however long you're on there for. Outside running is way better I find. Does anyone else prefer running in the rain (not heavy, but light rain)? I fnd it refreshing personally.
I definitely find it easier running outside vs on the treadmill, however I dont know if this is because when running on a treadmill i always run on a 3.0 incline to simulate road running (instructors advice)...
But a bigger concern for me is that I really dont like the idea or running a set route, for a 1.5m run I simply to 6 laps of a 400m standard running track, but think I would find it much harder to run a route.
When you run on a treadmill the momentum in the belt means you have to put in less effort for the same result as road running so if its on a higher incline your working your muscles more similar to if you were on the road (or so it was explained to me)
A track is OK for seeing how quickly you can run a mile, but in practice, you will never run a perfectly flat route; certainly every official run I've ever done has started with either a deep river or a big hill or one after the other. I hadn't done much running when soaked through and wearing boots, and I found it pretty tough, so you might want to give that a go so you know what to expect.