Thanks for this find!
Though they are similar in age and stature, both blonde and students - there are big differences.
First, are we even sure LS met with foul-play, IIRC as
cluciano63 pointed out, LS may have simply fallen into one of the open construction projects and been covered up the next morning...
I feel HB was more targeted - her abductor wanted her.
If LS, if taken by a stalker, seems spur-of-the-moment, opportunity.
LS was entangles with a number of "friends" around her that night.
HB was simply leaving her home to go to school.
If it's said that both happened in the morning hours, that's an apples-to-oranges comparison since HB was just leaving for school when it was light out and IWT had her wits about her.
LS was out late at night partying, drinking, drugs?, and then out alone in the dark.
Okay, can't resist making the wisecrack - where these two case are similar is that LE seems stymied...
ETA: 10 POI'S for LS, 0? for HB