+1 for along the canal. You can get on at Princess Street (having run down Canal Street) and head towards Trafford, it goes for miles. It isn't dangerous, our club members have been running this for years without any problems.
Starting to build up to 10 miles then hopefully 20. Not sure how much I'm going to need. I know the backpacks hold more, but it looks to me as though there's more material on those in contact with the body so might be more uncomfortable.
I've got a 220 and am reasonably happy with it. Gets signals quickly, is light and works well.
The pace alerts though are awful. They're all over the place, go off all the time despite me running a steady pace well within the range. I really liked the idea of these but had to turn them off now. Useless.