I think the sound level in the newer models are fairly comparable between wagons and open tops. My '06 open top Alpha of course is quieter than my previous '02 wagon. When purchasing, I drove both open top and wagon Alphas and could not tell much of a difference. There is something about the wagon enclosing the sounds from the rear versus the open top isolating the front from the rear than makes up for the canvas top. So to me they seemed about equal.

I would make a purchase decision based on what I liked versus what I thought was quieter...