If you only have time for one, I'd say the moderate intensity, 60 minute walk. High intensity is good for building muscle and increasing cardiovascular fitness, and it's definitely worth doing as you lose weight and get closer to goal. But no need to go all out on a daily basis during the middle of weight loss. Just my opinion.
__________________ "My religion is kindness." --His Holiness the Dalai Lama
There has been a lot of information about HIIT (High Intensity Interval Training) lately. Basically, you change up your intensity during your workout(low, medium, high repeated throughout). It actually results in more calories burned in less time without having to go 'full out' for your entire workout.
You can't out-exercise poor eating habits.