LSD versus HIIT

They may sound like the latest street drugs, but they're really two different styles of training. And I'm trying to decide between the two of them.

Long Slow Distance (LSD): These types of runs are generally reserved for the training of endurance athletes. I suppose, however, that anyone can do LSD training... it's just the "distance" is all relative to experience. LSD runs are usually a runner's "long" run of the week. Depending on ability, it can be as long as 20+ miles (or as short as 2 or 3).
Pros: Builds stamina; necessary training for anyone who wants to complete an endurance race
Cons: Not much of a fat burner; takes a long time

High Intensity Interval Training (HIIT): These are the types of cardio workouts recommended in Body for Life. They're generally very short--in BFL they last 20 minutes or so. HIIT workouts involve short bursts of "high intensity" (such as running so fast your guts practically fall out) followed by periods of recovery time (jogging or slower running). This pattern is repeated over and over again through the entire workout.
Pros: Torches calories in a serious way; short
Cons: Doesn't allow for much endurance training

So which one should I do?

While I really want to burn calories and shed some fat, I also want to get started training for some endurance events.

I think I'll try to combine the best of both worlds and do four runs each week.

1 LSD
1 HIIT
1 short, easy recovery run
1 "fun" run

That should keep my plan varied and interesting.