The main difference between the ISCO II and the Panamorph (other than one is available right now and the other should be available "soon") is that the ISCO shortens your projector's throw (makes your projected image bigger) whereas the Panamorph lengthens your projector's (makes the image smaller). I've never seen a live Panamorph, so I can't comment on optical quality, but I own an ISCO II and am VERY happy with it.
Some downsides of the ISCO compared to the Panamorh:
- It takes some time fiddling with focus, tilt, height, screen distance, etc. to get it perfectly adjusted. The results are great once you do, but the work is still there. Since the Pannie is composed of prisms, AFAIK
it shouldn't require nearly as much adjustment to get into focus.
- Removing the lens isn't something you'd want to do frequently, both because the lens affects the projector's focus which must be refocussed slightly, and because the lens is _heavy_. I understand the Pannie will allow the prisms to just slide away within the bracket for shifting between 4:3 and 16:9.
If you're already at maximum zoom and can't move your projector back farther, buy an ISCO. If you're at minimum zoom and can't move your projector closer to the screen, get a Pannie. Either way, if you can afford it, get one or the other. Moving from 16:9 letterboxed into a 4:3 display to 'native' 16:9 is like getting a whole new projector.