I would say it is an output issue. Check to make sure the air intake in the back isn't block by anything. Also make sure to wait to turn it on after you fill it up with fluid. It takes a while for it to get through the sponge. You should also be able to sneak a DMX and a power cable through the slot in the lid, I have on many occasions.
This video was shot about an hour after turning on a HZ-500 which is sitting just off down stage right behind the arch. Stage is 48' wide, 15' high, and 20' deep. With the wings and fly space added, it is more like 80' wide and 50' high. The camera was about 60' from the edge of the stage. Total house depth is about 120' and again about 80' wide. 20' high at its highest point (this is to the clouds, doesn't count the extra space above them). Roughly, that is 272,000 cubic feet. 'Visible area' is roughly 110,400 cubic feet. At 2,800 cubic feet per minute, that would take about 40 minutes to fill. The whole room would take about an hour and a half to fill. As you can see, the beams cut through even haze from the stage to the camera. And all this doesn't take into account the air handling system for a 1,000 seat theatre. If anything, I would say the HZ-500 is under-rated. If you are wondering what fixtures they are, the 6 across the back are HES Studio Color 575's and the 4 on the sides doing the gobos are Martin Mac 700's. And the video was shot on a crappy little Canon Powershot 8 mp camera. I can only imagine what it would like like on my 7D with the 17-35mm F2.8 II I just got in.
The other issue like you said is the HZ-500 puts out real, fine mist haze. The Unique is more like an Antari X310 (I also own one of those). To get the Antari to match the HZ-500, I need to set it at roughly 30-40%. That means somewhere between 3,000-4,000 cubic feet per minute. And once again, it isn't as even and more like fog vs haze. I haven't even really tried using the X310 for haze ever since I got the HZ-500. And there are times I still want another one for larger venues I work in (2,500 seat theatre which I am in a lot comes to mind).
Edit: Sorry, forgot that one was password protected. The password is Ariel.