I don't know how much difference there is in retarders. Maybe some, maybe none. I've only been using it a couple of months.
I use Createx but just because it's the first one I grabbed at the art supply store. It was around $5 for a bottle of about 6 ounces. Since I only use a couple of drops at a time I figure it will last a couple of lifetimes.
It works real well. It doesn't eliminate dry tip, but it really helps a lot. Where I've noticed the biggest difference is in using it for brush painting acrylics. I don't brush paint much, but I used to have a terrible time trying to brush acrylics. Adding a couple of drops of retarder to about 8 drops of paint and it doesn't dry up nearly as quickly.
And I agree that Mike's elixer is great. I also love the new name!