As has been pointed out by others there are several differences between the Panasonic PT-AE4000U and the AR100U. The 4000 is a more sophisticated projector with powered lens zoom and focus, Intelligent Lens Memory and Frame Creation 2. The 4000 also has better contrast at 100,000:1 versus 50,000:1 for the AR100U.
The main question is - are you willing to give up all these features for a brighter picture? Are any of these features important in your setup?
I own the AR100U and it is a brighter projector with great color and pop and a reasonable price at $1300. I've never seen the PT-AE4000U projector in action but upgraded from the Panasonic PT-AE900U that was not bright enough for my needs. I've been very happy with the AR100U and have over 2100 hours on the original lamp. I use it 3-4 hours a day so it's not a pampered projector that only sees action on weekends. My screen gain is 1.1.
These are all things to consider and not an easy decision.
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