Are prokaryotic cells usually longer than eukaryotic cells?

Nope,. It doesn't make any sense.
Actually Eukaryotic cells contain Organelles, which are lack in prokaryotes so Eukaryotes are longer than the parokaryotes.

In short, Your Answer would be "False"

Hope this helps!

Prokaryotic cells are much more smaller than eukaryotic cells because they are a much more primitive cells.

Because the carnivores keep the herbivore population in check