I've never used the red ones. I just don't like the look of them. They look like red LifeSavers.
I've been using the black ones for years. Unlike some vinyl grommets, these ones just don't dry out and crack.
Since they don't wear out and don't fall out easily, a couple of them last forever. Besides, I was able to score like 10 packages on clearance at K-mart for $0.25 a pack a few years ago back when they came two black ones per pack.....
The thing I like about the "Sampras O's" is that they dampen less than most dampeners. It's not like they silence your stringbed like bigger ones or worm like dampeners.
Those that say they don't feel little differences just aren't sensitive enough.
BTW, I think rubber bands dampen too much.
"The secret is to find your motivation every single time - your inner motivation - so I always want to improve myself..." - EV