My exercise includes long and low, long and moderte/hard, and short and very hard (intervals). I feel like they all have benefit. Plus the variety keeps workouts interesting.

I, too, had rejected the FBZ based on the same arguments of the OP. There is a line of thought, though, that points out other reasons than total calorie burn to stay in the FBZ. It goes something like this:

When you're at higher intensities you burn up your glycogen store. To replenish it, you eat carbs. Carbs trigger the release of insulin. Repeated exposure to insulin can be a bad thing. Plus most people probably eat more carbs than is necessary to replace lost glycogen, so the balance gets dumped on as fat around your midsection. Conclusion: Stay away from high intensity workouts (that focus on depleting glycogen stores).

Note that the emphasis is on repeated, prolonged, high-intensity workouts.