Hi Seth Ski-Woo!
Yes, it's true, many of Parks Sabers hilts are very cool to look at ... it is unfortunate that he is stuck on a dated technology.
To answer your question ... No ... his "duece" technology offers little improvement and is still not very impressive when compared to modern MR FX and Luxeon LED's. It is true that the blade does become slightly brighter when utilizing 2 9volt batteries ... but it's like switching from a 50 watt light bulb to a 60 watt light bulb ... nothing significant.
It should also be worth mentioning that Parks only offers this "duece" technology with one of their sabers ... it's the Graflex model (ANH Luke). On the same note, Lightech Industries has been utilizing 2 9volt's in most of their hilts for some time.
Basically if you stood there and stared at an ignited EL blade with 2 9volt batteries hooked up ... and you unplugged one ... you would notice a VERY slight dim of the blade ... and if you plugged the second one back in it would become VERY slightly brighter ... but if you werent paying attention you might not even notice. And yes I have done this ... many, many times ... I often stay up late with nothing to do ...