Whichway - Not really.  They are similar for the "Pure colors" (White, greys, and anytime an RGB channel value is 255), but not for other colors.  Take a look at BB's color and my Random Color.  This is why I included the extra results at 2.1 and 2.2.

It appears that HSV Exponential is a function of all three color values (which makes since from the name - duh....) and it is stable across the values.  What I mean is - the two colors in the top row of my render are BB's color (255, 128, 64) {the orange} and the same values, just in a different order (64, 128, 255) {the blue}.  With Exponential tone mapping the channel values were consistent and independent of each other - for a given tone mapping level a channel value of 128 will always map to the same value no matter what the other color channels values are.  With HSV Exponential, that is not true.  Compare the values returned for Dark Grey with the Green Channel values from BB's color.  And while I didn't list the blue version of BB's color in the above table, it's values tracked exactly with the orange version, just with the Red and Blue channel values swapped.

Give me a few minutes and I'll get some samples from some of the other squares.  (I was only using the right hand column from my original post for these results as well).