Cindy, here are two excerpts from the "frets" article linked above, which address the tone issue. Read the whole article to put these into perspective (or if you have already, my apologies, perhaps this doesn't quite provide what you're looking for).

"There's quite a bit of disagreement over the effects and benefits of one bracing system over another. We all agree that IF ALL THINGS ARE EQUAL, namely same maker, size, style, material and age of guitar, that the scalloped brace instrument will have more bass response. It's predictable, since bass response is generally increased if the top is made more flexible, and the scalloped braces are more flexible where they are cut lower."

"Straight brace guitars are not necessarily inferior. Some players prefer the sound of Martin instruments with the straight braces. These pickers may refer to bassy sounding scalloped models as being 'tubby.' Of course, the scalloped brace Martin player might call the straight brace models 'tight' or 'tinny.'"

Other parts of the article give an historical perspective which sheds some light on the "marketing hype" angle.