Is the dual the three channel or two?
I have a single rec (Rectoverb), and i think its fucking great. My experience wtih the dual rec is limited though.
The dual will have more head room, and the options for swtiching between EL34s/6l6 and choice between Diode/Tube rectifier. Chances are, though, if you're playing heavy shit, you'll use diode anyway, and most likely 6l6s.