I use both.
The differences between the two aren't huge though.
Here's how I have settled in with each disc:
Approaches and short drives:
I use medium Ions for most short-ranged control shots that curve.
They give me a really nice left to right flight when thrown RHBH and good right to left when thrown as an anhyzer flick.
I go to the Anode when I want a little more distance or a straight shot without much fade.
From what I can tell, the Anode likes to go straight and, in doing so, will compensate for any minor form flaws better than the Ion.
Putting:
Inside of 20 feet, I don't see a difference.
Outside of that, I have been committing to the Anode because it doesn't tend to fade out as early, allowing me to go straight at the basket with more confidence.
It also tends to stay up for me better and not facemask as often; the Ion has a tendency to lose altitude very quickly for me sometimes.
I'm not sure how much of this is real or perceived or whether it is the bead that alters my release slightly, causing me to miss low.
If I need a left or right hook on a putt to clear an obstacle, I'm using the Ion.
Stiffness:
I've always been more partial to the medium stiffness.
I feel like the soft deforms more for me on a pitch putt and gives me a less consistent release.
I did switch over to the softs for a brief time earlier this year and had good success.
They seemed to have a little more short range glide than the mediums when given a good release.
But, once the temperatures started to get up into the 80's and the softs got even softer, I switched back to the mediums.