I use a hybrid for the best of both worlds. Fltpln for planning an filing, ForeFlight in the cockpit.
Things I like about Fltpln:
- As others have said the planning accuracy seems to be much better
- Previous routes and such seem better and more complete
- Way easier to manage a pool of upcoming flights
- The plan printout is much better with a lot more info in a more efficient layout (even with the adverts) than what happens if you try to print out your nav log. I use the iPad mostly in flight with FF but I always have a paper printout from FltPln
- Various other little features like being able to automatically fax the FBO at your destination with your flight details. I've seen people at the FBOs with my fax so they definetly use it to know I'm coming. Helps having people know I'm arriving and will want fuel at a certain time without having to make calls.