I think Futaba changed to the push button because guys were complaining about the toggle switches getting broken off. I have two old Conquest 6 PCMs with the toggle switches broken off and I don't even know when or how it happened.

The newer push button seemed a lot better... for about a minute and a half!! I hate that thing, especially when the student can fly pretty well and I have to hold it for a long time. I would replace it with a switch from Radio Shack as N7OR said.