My first daughter was super picky about the brand and style she would use. My second daughter will take any pacifier at all - and she's two. She never cared if it was "natural" or "orthodon'tic." Depends on the kid.
My son didn't notice the switches and I switched it 3 different times I noticed that he didn't like the first stage. It took him for ever to get it but once I gave him the 6 month one he loved it he still using it and he is one. It's almost time to start detaching him now.