As of October 11, I have three varieties ripe with the fruits dropped from the trees. Coolidgei is my oldest feijoa tree planted in 2001. This tree might be the original Coolidge, as it has round fruits. However I bought it labelled as Coolidgei. The other two varieties are Marion (the fruits turned out to be from rootstock under Marion) and Kaiteri. These are small trees planted couple of years ago, and they produced just few fruits this year. In the picture below, Coolidgei is top left, Marion (the fruits turned out to be from rootstock under Marion) is on the right, and Kaiteri is at the bottom.
My favorite out of this three is Kaiteri. However, I was surprised to hear that my son prefers the old plain Coolidgei that has significantly less soft matter in the fruit, and more acidic than Kaiteri. All these are good fruits.
Below are the cut fruits, left to right: Kaiteri, Marion (the fruits turned out to be from rootstock under Marion), Coolidgei. All Kaiteri fruits have darker flesh. They are not overripe.