I would like to know the brightness level comparison of a calibrated plasma and a calibrated fp.
The plasma wins every time (well unless you want to get up to 10s of thousands of $ in a projector). Projection needs a dark room. You can watch with light, but the picture will wash out much easier than with a plasma. A plasma essentially works with any artificial light. A plasma will of course wash out in direct sunlight. A projector needs controlled light (i.e. no light shining on the screen). Best results for a projector is no light in the room.
Of course you can see the image and watch it with lights on in the room, but you will not be fooled in any way shape or form that having the lights out would be much better.