I know they already answered, but as I'm doing the Higdon plan that's how i do mine. It's more of a progression run where it's 10-15 min of warmup, then a steady increase until you hit 5K (or 10K pace for this HM training), hold it for a few minutes, then back down and a short cool down.
There's a little more flexibility with it and going with feel but still challenging. I like them. But the other tempos described above I'm sure are more difficult and easier to do in that you don't have to think about changing paces. What I like about Higdon is I can feel what the different paces are like and that in itself is helpful for me as I'm still learning those and how I do with them. Right now, it's my favorite type of run and the workout I look most forward to doing.
Here was my last one with a peak at 7:50 pace for a few minutes