We always like the park hopper. Like others have said, we LOVE the ease and flexibility. We go during Christmas, so it's kind of imperative to have it due to the chance of park closures, but our reasoning is pretty general.
Let's say there's a day where you want to do Magic Kingdom, but EPCOT has EMH - with the park hopper, you can head to MK during the day, and still get to experience EPCOT for EMH.
It's always very useful on longer trips. Let's say you do an 8-day trip. By day 5, you've been to all the parks. There's only a few things you missed at MK, DHS, EPCOT and AK. Well, you're not gonna go to MK for a full day then! You can go to MK, get the last three rides or attractions done, and then head to AK to finish those three attractions... and so on..