The advantage is that you can knock down these high risk targets early before the ball save even starts - - if you soft plunge properly and cradle on the right flipper the ball save will not activate until you hit your first shot, maximizing the time you have to knock those targets down and get your outlane ball save lit and ready for later in gameplay.
For me, I try to soft plunge and then go for the Targaryen shot as much as I can since this is the toughest shot for me on the game.
Also, if you have a premium or LE, if you soft plunge, light a mode, light a lock, and then go up the middle to lock the ball and start the mode, when the subsequent ball is kicked to the shooter lane the game will autofire it and then bring it up to the upper playfield making collecting a castle much easier and quicker than having to try and make a right ramp shot to get it up there - it's sort of a gimme way of getting the ball risk free up to the upper playfield and getting all the extra benefits of what the upper playfield has to offer during modes. It won't do this if you plunge the ball too deep right off the start and send it up to the upper playfield to begin with.