The poll is slightly misleading because most if not all display devices are doing some of their own conversion/scaling or have built-in compromises.
For example, feeding a 1080I or 720P signal into an XGA projector will cause further conversions of the signal even if the projector "accepts" the signal.
If you have an STB that converts everything to 1080I and then you feed it into such a projector, it is not clear whether that is better or worse than an STB that will generate a native 720P signal.
My point is that one needs to consider all of the devices that are in the signal path to know which ones, or which combination, may be responsible for the loss of quality.