Incline makes a difference in calories burned in either activity, so walking on a paved road on an incline (or on a treadmill) will burn more calories than walking on a flat road. Hiking to me involves a trail or unpaved road, this makes it more difficult than walking on a paved surface, you have those lumps, bumps, tree roots, rocks etc to deal with, so balance comes into play more than walking on a paved surface. But some hiking trails are paved as well (example, Zion NP has many trails that are paved, even if they are not maintained...) but still hiking because of the nature of the trail (switchbacks and incline)
Like the other posters have said, you really can determine for yourself the effort you put in, and decide if you want to call it a "walk" or a "hike". Either way, enjoy it!
highest weight ever:202, SP starting weight: 143
New goal: 125 lbs, just to see what that looks and feels like! Hit it: Feb 2013!
H: 5''4" 49 y.o.
"Don''t let yesterday use up too much of today." Will Rogers
"Eat Food, Not Too Much, Mostly Plants" Michael Pollan
| current weight: 7.6 over