Choose fondant 95% of the time! Fondant makes your cakes look perfectly iced, whereas with buttercream icing you may see lines from the decorator trying to get you icing smooth. Also you may see air bubbles because the icing was over whipped or to cold when your cake was iced. Fondant will give you a perfect look with the exact details you are looking for in your cake. While with buttercream nothing will be exactly be the same because everything is being done by hand.
Everyone says fondant taste horrible well that’s just not true! Maybe they have just never had good fondant or even decently priced fondant for that fact. What they sell at convenient stores probably does not taste good, but bakeries do not buy that stuff. Most bakeries pride themselves on having their icings and fondant tasting good. They do not want to hear that people just peel off the horrible tasting fondant. So if the owners would not eat it, I’m sure you won’t find it at their place. Fondant is like buttercream everyone has their own recipe.
Fondant will cost a bit more than buttercream, however it is not a significant difference. Most bakeries charge an additional $1-2.00 per person for fondant depending on decoration. Now not all cake should have fondant on them. If your cake has a ton of piping or flowers that will cover most of the cake just get buttercream. There is no reason to get a perfectly smooth cake if your going to cover it all up.