I don't know where you got the idea that presses had more down time. I personally don't think I would suggest that in a conversation with a printer. I also wouldn't suggest that your quality is better because it's not. A press also can run any color anytime without a $1,000 cylinder requirement for each color. They also have less registration issues than we do.
Keep in mind that a press could be $30,000 or $300,000 or $1,000,000 plus so it kind of depends on what type of press you are being compared to.
There is a point where-by a run-length is long enough for a press is cheaper (set-up, make-ready, etc. all taken into consideration) but every operator is going to have their own idea where that line should be drawn.
Your advantages are:
No dedicated, experienced (and possibly unionized) pressman required
Little to no make-ready
No clean-up..."instantaneous color change with no residue left from the previous color"
Easily switch from paper to envelopes, etc.
Unless someone is trying to eliminate their press or keep from buying one, I never suggest that the duplicator replace the press but that they should co-exist.
I've gotten alot of good out of this analogy...
"Every farmer I know has a passenger car, pick-up, and a tractor. Why is that? They each are gas powered, run on four wheels, get from one place to another...why the need for all three? Well, can you imagine hauling hay to the back 40 with a passenger car? Sure, it can do it but it wasn't built for that and won't hold up. What about taking the tractor...way too slow. That's why he has a pick-up...for all those jobs too long and hard for a car but need to be done quicker than a tractor.
You Mr. customer, are like a farmer without a pick-up. You are doing hard jobs with a passenger car (Copier) and quick jobs with a tractor (Press or outside printer). You need that pick-up in between."
Good Luck