In fifty matches against champions, this went 26-24. And the one unupped log is because the microscopic unupped bonus amuses me.
With the unupped version, it helps to kill something early to feed the soul catcher, thus generating the quanta to play the rest of the things that benefit from death.
Upped and unupped, using a late-game plague on your mushrooms for the burst damage. While doing the unupped, bursting with plague late-game was vital to take down Xylene. As with all epidemic/log variants (see Cat-a-log, posted in the Team Card Design event), it is highly vulnerable to permanent control.
I feel like there are more experiments to be done on quanta flow for both upped and unupped (PPM vs soul catchers), and potential for empathetic bond variants, but I am not nearly methodical enough to do all those tests myself. If anyone wants to experiment, feel free (and bonus points if you avoid the Generic 30-card Rush format).