Hi Tony
I don't have any experience of the fully battened sail. I am sure it gives better shape and may stop it flogging about in stays. I have heard that full battens can make it more fiddly to bend on the sail in the first place. I think fully battened possibly looks a bit better than the single high full length batten I have, but not enough to make me want to change.
One very useful use of the full batten last year was poking out a stone that was jamming my centre board! I just couldn't shift it by banging the board and thought"If only I had a long, narrow. rigid strip of something to poke down the slot", and then I remembered that I did. Only took a minute to get it out of the sail and it worked a treat. So now my batten justifies its presence on the boat, with at least two uses.