It looks like with these W2700/HT3550 projectors we are really getting something like 1080p+ rather than 4K, possibly situation is similar to Epson 'fake 4K' implementation.
I do not have W1070 to compare at the moment, but I would be surprised if W1070 was sharper, although as we saw this can vary wildly from unit to unit.
At this point, I am not sure if the problem is with the lens or something went wrong with XPR implementation - on my unit disabling silence (so engaging XPR) mostly makes the picture blurry (removing 'screen door effect', which is great) but it adds very actual little details to the picture.
I would not even have a problem with this, if not the case that other manufacturers/models can extract much more from XPR technology - and it gets much closer to the 'real 4K' . (it is probably just poor lens on BenQ...)
Let me just paste one more comparison, this time including the 'reference', being 4K OLED:
For OLED, it is of course a macro photo of relatively small display, so screen door effect is crazy and fill factor is insanely low - and colors instead being uniform, can be now seen as individual subpixels.
This is also good demonstration of one of the biggest strengths of projectors: there are no subpixels. Each pixel is completely filled with one very specific shade of color (though temporal trickery with color wheel or by passing the light though multiple filters in 3LCD-like desings), which gives this smooth, organic, 'borderless' look we all love.
When it comes to resolution though, you can clearly see that all the details are there, as demonstrated by OLED. In comparison, both of these '4K' projectors look like crap - however, one is crappier than the other.
For instance on Kratos leather armor, there is this complex embossed pattern - which you can actually still see on UHD300X. On BenQ though, there is just this murky goo of 'something'. Also, what the hell happened to Atreus face?? It is almost melting down.
And you might think all of this are just a small differences, but they do make impact in real life viewing. UHD300X just pops with 4K content, objects are sharp, detailed and crisps. BenQ looks OK (especially on its own), but you just missing this extra clarity and definition side by side. As someone perfectly said, it is like watching with dirty, greasy lens.
It is not like W2700 it cannot deliver good picture, but the fact that there is this weird resolution handicap specific to W2700/HT3500, which does not have to be there (as proven by other models) is immensely frustrating - WHY BENQ??
Regarding reliability, I get that projectors are complicated, fragile opto-mechanical devices, produced at relatively low volume compared to TVs and it is much easier to guarantee reliability and quality when nothing moves and no complex optical elements are required.
Still, it feels that QC should be even more strict in such case, as for projectors there are many variables and things which could go wrong. Possibly this is a calculated thing and it is just cheaper to replace faulty units when people complain than to implement sophisticated QC process, but if feels that it hurts brand perception. Other manufacturers got this problem as well, but situation with W2700/HT3550 seems to be on the extreme of the spectrum.
There is also case of expectations from 'normal' people when it comes to performance of these units. For example there was a photo of W2700/HT3550 menu posted a few pages back in this thread, with absolutely insane amount of CA (probably even more than in my initial unit?), but OP was not even highlighting this as a problem, so likely quite a lot of people are OK with these defects and only crazy OCD enthusiasts like a me actually care...
ALSO, BONUS PHOTO:
W2700 with 1080p input vs 4K input. I would say the jump between those is almost as substantial as between W2700 4K and UHD300X 4K...