Personally I love bottom side up. I am still a new baker, and I think it helps me get the best overall look with the cake. If my cake domes while cooking, I can cut the dome off, and flip it, so that I still have a perfect surface for the top of the cake. I've also been told to 'crumb coat' a cake before icing & decorating, to prevent having the issues of loose crumbs, although to be honest I haven't tried this method yet. Good luck!