I'm not sure what is bringing the volume vs intensity debates to the surface right now, but I'm getting lots of questions about what is more valuable, increasing training volume or intensity?
The answer depends on your current fitness and goals.
1) If you don't have the endurance to complete an event, then first you need endurance (volume). Heading into very intense workouts without a fitness base increases your risk for injury.
2) If you already have an endurance base, then whether you add more volume or intensity depends on what you are currently doing and your race goals. Let's consider extremes because the issue is easier to see. If you are currently training 10 hours per week, with your longest workout at three hours and your goal event is two-hours long then strategically adding more intensity will likely bring better results for you than adding more volume. If your goal event is 12-hours long then more volume, particularly focused in your long workouts will do you more good than more intensity.
To say intensity is better than volume (or vice versa) in all circumstances is like saying a table saw is always a better tool than a nail gun when you're building something big. Or, a table saw is the only tool to use when building something big. Makes no sense.