A quick video A/B with the Friedman Runt 20 and the Runt 50. Back to back, and played through the same cabinet with (pretty much) the same settings. You can hear that the 50 is a bit louder and pushes more pressure.
Friedman Runt 50 Video:
https://www.youtube.com/watch?v=sv_rD7eCEaM
Friedman Runt 20 Video:
https://www.youtube.com/watch?v=Apjp7MxvwrU