No surprise, the Epson tackles really dark scenes, really well. I figure you are going up $1000 to find a projector that can do as well, or better, and it mostly blows away anything that costs the same or less (in terms of handling blacks). Being a black level fanatic – looking for the projector that really shines when handling really dark scenes (not brightly lit city nightscapes) – I knew going in that the black level performance of the Home Cinema 5050UB is a cut above - any projectors that cost the same or less, would prove unmatched. The closest tries would be the older, just discontinued UBs. BenQ's new HT3550 (DLP) (which I like for folks that can't afford this Epson UB), also has a dynamic iris, and is a lot better than other under $3000 DLPs to date, but still no match for this Epson.
It’s true that when there’s more than very little ambient light present, that the differences when viewing two projectors with different contrast and black level performance, that the differences are noticeably diminished by the ambient light.
So, to simplify: If you are going for a living room, media room, family room type of setup with less than perfect lighting control, you will not get the same extra bang for the bucks on really dark scenes, if you choose the HC5050UB instead of the less expensive HC4010.
However, if you are putting together the classic home theater/man cave (ok, in this day and age, let me amend that to “person or people cave”), with dark surfaces and great lighting control, I’ll always recommend spending the extra for the better black level performer, in this case because prices are reasonably close, and you should get a number of years enjoyment out of your new projector! If your room is mixed - less than great control in the daytime, but really darken-able at night, then for that nighttime viewing you'll get the full extra benefit, even if you get a slighter benefit with some room ambient lighting.
The images in the first player are the usual black level / dark scene images. I’ve included several, but then we have the intentionally overexposed (and greyscaled) “Bond night train scene” image from Casino Royale. In general, exposures do vary, but you are looking for the image with the most pop – where the lightest parts of the image are extremely bright while the darkest parts are still very dark. The letterbox below and above gives you an indication of how black those blacks are – relative to the whitest parts of the image (i.e., the train’s front light).