Just done W6R3, and have reached that run so far mostly on a treadmill. Outside recently I have struggled, probably by running too fast. Today however was a glorious day and I did W6R3 on a sunny Douglas Promenade.
I felt I was just chugging along and struggled to keep going at halfway, but did, and again at about 20 minutes, but continued the chugging. Did 3.47 miles including the walks in Laura's 35 minutes, in a pace just over 10 minutes a mile.
I am fairly certain that on the treadmill I would not have been tempted to slow down, and would have had a slightly higher pace.
Conclusion? Running on a treadmill is easier - and maybe my feeling of cheating a bit is justified
I miss the control of being able to up the pace on the treadmill when you feel comfortable - not so easy when you are outside and gasping and frightening the horses and passers by.
But whatever you do, it is better than sitting at home