For me, VideoDrive wins hands down.
1) Go to the Queue tab in Preferences and click the "create hot folder" button. Choose whatever folder you want as an 'inbox' folder for new videos
2) Select if you want to process new videos immediately or after fixed intervals (I prefer the latter and set the number of minutes to 120)
3) Check "Never ask confirmation to save metadata". Otherwise it will show you a confirmation window blocking the import process.
4) Check "Automatically requeue videos". Otherwise if you are copying/downloading big files, VideoDrive will try to import them but fail as they are not complete yet.
That's it! As soon as you have a new file, VideoDrive will do it's thing and put the file in iTunes. 😀