I have both the Ironball and Mark V:25.
For bedroom volumes, the Ironball is easier to set up and sounds still great at lower volumes. Also, the power soak does really work. You'll loose some deep-low end in the 5W and 1W settings though, but in the 1W setting, you can crank the Master a bit, which gives it some added 'feel'.
Mark V:25 is way more fussy and a hair difference on the volume knob can make it go from whisper quiet to 'ouch, I hope my neighbors are in a forgiving mood now'.
Nevertheless, as far as great cleans and that Crunch mode go, the Mark has the Engl beat. For a more easy to set-up high gain tight metal tone, the Engl has that over the Mark.