The Evo and EVO+ are essentially the same release with the exception that the EVO + has the ITS system. It allows you to change springs without having to open the case of the release. On the regular EVO, you have to open the case to do that.
The revolution is also essentially the same internally, only it uses a pinky trigger safety instead of a thumb safety. I only got to try one of these for a short while. I have meaty paws and I kind of liked the feel of it over the feel of the EVO, not enough to buy one instead of the EVO though.
If they had made it when I got mine, I would have gotten the 2 finger EVO instead of the 3 finger...but then I like a 2 finger release (thats what I shot when I shot hinges)...
All 3 work essentially the same. You probably will have a hard time getting a new EVO, but prices on used ones are better than for the EVO+. If you have a pretty set holding weight, there really isn't a big advantage to the EVO+ so I say save the $$$ if going used...
Hope that helps...