Indeed PHJim... that point is debated constantly over at Mandolin Cafe. The consensus (and my view also) is that there is no difference between the sound of a carved top F-style and a carved top A-style with F-style soundholes. While most bluegrassers prefer the F-style (Bill Monroe played one!) some musicians like Tim O'Brien play bluegrass on an A-style. The carved top oval hole style does, however, have a different projection.

So it's really an aesthetics and tradition question. I personally prefer the clean lines of the A-style but many others prefer the F. Making a scroll certainly adds a lot to the price if that is a major consideration (seemingly not for some given the cost of some high-end individual luthier-built F-style models).