I'd say do a little of both, sprint and walking. I personally enjoy walking on days when I just feel beat. For example, when I hit squats a whole lot and the next day just feel a bit drained I think walking is great. When feeling strong and enthused, then sprinting is my thing. All in all, I go with how my body feels.
I prefer uphill sprints of about 15-20 yrds of moderate incline. When walking I usually do it at home as I have a treadmill and go about 2.7mph on a 4-6 degree incline. I use the treadmill/walking in the morning in a fasted state as I wake up at 4:00am and can't leave the house - I have a kid sleeping and can't leave her alone. Other days I enjoy outdoor walking just leisurely or up a steep hill I have near my home.
Or, pick up a jump rope - you can get a quick, but intense workout for sure if you do intervals of varying speed/time.