Again, I'm not making this up - it's at least 256k colors vs. 16M colors when playing video.
Can the eye see the difference in the real world? Oh, you betcha and more.
Can the eye see the difference when downsampling an HD source that really has that color range to an ED screen and can the eye discern that on such a small screen? That will vary by individual - and it will vary A lot - and it has nothing to do with eyesight quality as much as program content.
It's not that the SAMOLED screen is set so much to an HDTV's Vivid (or equivalent) setting - it's that it can go a bit brighter and when demo'd in that mode, it pops. Like a TV on a showroom floor, you won't watch your videos at that high setting. Adjusted for the same brightness, the difference is one of errors - the Evo will be wrong in one direction, the Samsung in the other.
Because they both lack gamma adjustments.
Where the SAMOLED really might make a difference in that pop-ability is for playing games (vivid cartoon colors anyway) and for using as a phone or web reader in a brighter light environment.
The other place the SAMOLED makes a difference - less power consumption when putting out the same amount of light than the Evo.
I'm lucky - I took an Evo and a Samsung and cued up the exact same video (720p) on each and same on my properly adjusted HDTV - holding each phone at a distance so the relative size to the eye was the same as the HDTV at a distance - and each at a subjectively adjusted matching brightness.
Under those conditions, they were both color-wrong compared to the correct HDTV source.
Side by side without the TV source, I thought the SAMOLD looked better. When comparing each to the HDTV, the SAMOLED was exhibiting black-crushing. So it looks more contrasty and less washed out as the Evo in a quick comparison - but there ain't no such thing as a free lunch.
It's a tradeoffs of errors where color accuracy is concerned.
If you brain, intuition or your eyes say the Sammy is the way to go, then go with the Sammy - it's _your_ phone.
But the marketing myth that the SAMOLED is more accurate is simply that - a marketing myth.
They're equally in error, so choose the one that pleases you if it's down to screen selection.
If you take the Samsung route, and have lingering doubt of what I say, then your other take away is that compared to the older AMOLED screen, the SAMOLED is much better.
The tests I did said the Evo was a bit red heavy while the Sammy was a bit blue-heavy - while a friend across country doing the same thing said the Evo was blue-heavy while the Sammy was red-heavy.
And that's the outcome of unit-to-unit manufacturing variations when we have no chroma adjustment for either one.
Not as exciting as what fans on either side will argue - but the boring truth, in simple manufacturing and engineering terms.
Both sides have ardent followers ready to defend their favorite because in truth, the Evo doesn't wash out and the Samsung doesn't over-saturate (like the earlier AMOLED did). Simply a case of complimentary errors - the actual color truth is in-between any two units you'll try in the real world.
Hope that helps, and I'll leave you with this advice - when viewing subjectively, trust your gut - you've got to live with your purchase, and it's your gut.
PS - I didn't have the selection when I choose the Evo. Now that I do, I'd still choose the Evo - having nothing to do with the screen, but the devices other feature differences.
Your mileage may vary - or may be the same.
And by the way - my eyesight is quite good when adjusted for astigmatism.