Originally Posted by Mojo_LA
Sadly, most of the market perceives "quality" in very simple terms (i.e. 720 is low quality and 1080 is high). Even on this forum, so many people rush to get 1080, not realizing that a 720 model with better contrast, optics, etc, could have far superior picture quality. But "1080" is the perceived high end, so that is what many people will focus on.
I wouldn't entirely agree with that. 1080p projectors in general have better optics and contrast and superior picture quality than 720p projectors.
1080p projectors need to have better optics to take advantage of the higher panel resolution
The imaging chip (whether it is LCD, DLP or LCOS) are usually of a newer generation than their 720p counter part. You'll find that most reviews found that 1080p projectors have visually better PQ (less SDE, better contrast and black level, more picture depth etc) and measured performance (contrast and black level especially). the only exception is probably the Optoma HD81, which is a poorly designed projector, with significantly poorer picture quality compared to other DLP 1080p projectors.
The only major advantage of 720p projectors over 1080p projectors at the moment other than price is probably light output. You can find reasonably priced 720p light canon like the Epson TW700, Cinema 400, Panasonic AX100 which can produce anything from 1500 to over 2000 lumens. 1080p projectors can only produce in the region of 1000 to 1200 lumens at the most (if you don't count the really high end 1080P 3 chips DLP models).