Gut,
Where you'll notice any difference, if at all, is probably with the "toothpick thin" sporter barrels.
Each barrel, no matter how thick or thin, has vibration characteristics known as "barrel whip".
In a sense, it acts almost like a tuning fork vibrating when a bullet is shot through it. Microscopically, if the muzzle of the barrel is viewed when a bullet is shot, you'll actually see it oscillating.
The thinner the barrel, the more it oscillates, the heavier the barrel, the less it does so.
Each barrel made, even if exactly the same in profile, and coming off the same manufacturing line, have different harmonic properties, otherwise known as "barrel ring".
This "ring", or "harmonic sweet spot", is where a given load needs to be on a consistent basis to shoot it's best through that gun barrel. The less a barrel vibrates, the more apt it is to shoot most loads well, or better.
If you picture the vibrating oscillations of a barrel as numbers on a clock, if you get a load that falls within the barrel's sweet spot, and the load is consistent, it might exit the barrel, very consistently at say 11 o'clock, 12 o'clock, or 1 o'clock. An inconsistent, or inaccurate load might exit at all three positions during a shot string, and thus failing to give decent accuracy.
Simm's De-Resonator trys to dampen these harmonics, or vibrations, as does the BOSS system. Out of the two, the BOSS system seems to make more sense in that it can be "dialed in". How good it works, I don't know. Never tried it.
Hope this helps,
Bob