We lean towards the parks since there are no sidewalks in our local neighborhood. The neighborhood is very pleasant, but having to walk in the streets, particularly with enough teenage drivers around, it not something we want to do often.
We have 2 parks within a 10 minute drive that have long walking paths, so we do that often. There is also a golf course less than 10 minutes away that, though closed for a couple of years (shame, as I liked to play it), you can still walk the cart paths as it is built within a residential neighborhood.
We will also drive to the nearest small city about 15 minutes away, they have a nice set of connected parks and paths that one lap is 5+ miles. The paths go through downtown, along water, through woods, etc. so lots of variety. It is also easy to find free/cheap parking along the route. Many times I arrange to meet friends in that city for a meal, but go early and/or stay late to walk and see the sights and sounds.