It's what feels right to you. I've done buttercream and it doesn't firm up enough. A friend swears that more meringue powder solves the problem. Dies that make it frankenfrosting? Glaze takes a long time to dry and it has limitations. A friend told me you can't layer it to do things like noses. I like Royal icing. I like that it dries hard and I like how it handles. It can be frustrating if you get bleeding or blotches, but most of the time it works well.