The one and only time I have run a half-marathon, I made a poor wardrobe choice that lead to some uncomfortable chaffing. What I wore had been great for shorter runs, but at that distance I simply needed something different. So, take my advice, and consider your distance when making any wardrobe choices.
For just a few miles, the fit of most pants will likely be perfect. If you plan to run more than an hour or more, however, we recommend that you take comfort and fit carefully into consideration.
At longer distances loose-fitting is likely ideal. The less rubbing against your skin, the better.
When training for marathons and half-marathons, consider training in the running pants you want to use before the big marathon day… trust me.