both are effective.
long slow distance running at a light pace on a soft surface is going to put less strain on your body than doing high intensity interval training
i actually found that when i was training as a runner i stayed healthier doing 40-50 LSD runs vs. doing interval training on a track, and i also improved my endurance far better. also nobody who trains for endurance just does interval training, so it isn't like i am some weirdo.. they might throw that in once or twice a month
if time is an issue you can do 15 minutes of HIIT, then stretch out. just don't over do it or you will end up with injuries and invest in good shoes