Both training principles have pros & cons, lets look a little further into each of them & break them down so see which have the most benefits.
HIIT training (high intensity interval training)
HIIT exercise sessions generally consist of a warm up period, then several repetitions of high-intensity exercise separated by medium intensity exercise for recovery, then a cool down period. The high-intensity exercise should be done at near maximum intensity. The medium exercise should be about 50% intensity. The number of repetitions and length of each depends on the exercise, but may be as little as three repetitions with just 20 seconds of intense exercise. The specific exercises performed during the high-intensity portions vary. Most of the research on HIIT has been done using a cycling ergometer, but other exercises like running, stair climbing and uphill walking can also be effective.