The difference is Pompeii is larger. However, few of the buildings in Pompeii have surviving upper levels. This is because the initial pummeling of pumice rocks and boulders fell there. Because of it's size and its level of destruction, Pompeii can be sort of oh. Same thing. Same thing. Same thing. Ditto. The buildings in Herculaneum are better preserved having been buried deeper in ash. However, in Herculaneum, there are no casts of the bodies, only bones. This is again because the initial pummeling of rocks did not fall there so fewer were trapped and those that were left were vaporized down to the bone by the pyroclastic flows whereas those in Pompeii were covered and thus casts of where their bodies were were able to be made. There is also more shade in Herculaneum.