I don't know about babies, but I did try my younger horse in a french link when I first got him and he really didn't like it. He chewed and fussed so bad I almost couldn't stand to ride him. Got his teeth done, same thing. So, I decided to search for a new bit for him and decided to try one of the Mylers with the barrel (he seemed like he didn't have much room in his mouth and they take up less room) and all of the fussing stopped almost immediately.
Also, my older thoroughbred actually likes his regular snaffle ( I do try to ride with really soft hands and try to never pull to the point of causing the "cracker jack effect). I tried him in the french link and the Myler and he fussed about both of them. Go figure.
So, I guess the point is - you might need to see what your horse likes - they may or may not like a french link.