I have one layer of Brown Bread in my trunk, doors, rear panels, and hatch lid. Not a lot of sound outside the car whatsoever. Definitely no rattles.
Brownbread is cheaper than Dynamat and does the same job, so I would recommend it. I don't see how the adhesive properties are different, I've used both, they are basically tar and rubber and will both stick to anything. I run my car in winter and summer and never had a problem. And I have it upside down and on the sides.
If you need to use different kinds of Dynamat for upside down and vertical surfaces, that just means that they don't put any quality into their Original product and overcharge for their Extreme. Brown Bread works on ANY surface at ANY angle.
And I am not a Brown Bread rep
-Diabolik