Other than in looks I don't worry about the buttons. Their reliability seemed generally good to me but I have no idea what happens in year 10, 15, 20 . . . .[and these things are now long in the tooth, first made in the 80's]
If your existing Yamaha seems to have no audible distress at the levels you use it at and you don't hear hiss, I don't think there are any good reasons to swap it unless it lacks a feature you want (or breaks).