Neither actually - whats better for me is eating Haribo whilst watching TV, however, I am trying to embrace getting fit, losing weight and generally being a more sociably acceptable size!! I've been overweight all my life so I think I've put enough time and effort into this experiment of seeing how life is for fat girls. Quite frankly, other than retaining heat, remote controls and crumbs down your cleavage - its not always been fun.
So back to the question - what is better for me - running or walking? Well, running is a great and basically just an extension of walking! It is for me, I think I road run at 5.5mph which is not a fantastic speed but then I'm not in any hurry. I'm still amazed that I can run, I never knew that was what my legs where for. Stick me on Roger (my treadmill) and I can belt out 7mph and even maintain 8.8 mph for up to a minute. However, its challenging and there was no way I could just start running - I had to walk first.
Both activities are focused on the lower body muscle groups and there is no massive difference in the amounts calories you burn. Medicine & Science in Sports & Exercise did a study in 2004 - they found on average 1 mile of running spends 113 calories and walking a mile spends 81. The only real difference is that your spending your calories quicker.
Here's another fact for you - and girls - this is why you should get a sports bra. A force equal to 4.5 times your body weight is put on your heel whilst walking - this force travels and turns into jelly wobble and can give you a nasty injury. But think on and consider this, it raises to 9 times your body weight whilst running! You don't want them by your knees, in your eyes or over your shoulder, so harness them!!