Dont laugh, i use a lenova yoga tab pro as my projector, it recently came in very helpfully at hospital when i was laid on my back after a operation. i watched mobvies on hospital cinema with blue tooth headphones lol. Basic thats all my experience with projectors is.
I say that cause i have set my room up ready for the uhd512, including ikea floating shelfs for me denon amp ps4 xbox s for 4k playback lol and my pc.
Basicly i nearly changed my mind when the 3550 came out, after all it had better black lvls than the optoma uhd51, as it uses a mechanical shiris or something, instead of the 51s lamp control, thats a bigy to me, then threes the smaller light border, something im not that worried about as im not gona be painting my walls black or anything like that. But then there's the sharpness. Majestic tells us in 2018 the optoma uhd51 is probably the sharpest projector using that particular chip, a chip different from the 3550 and thats in 2018 the sharpest projector. For majestic to say the benq is fine but you sometime wish it was sharper seems to be a real thing here and a directly feeling comparison from two opposite sides.
Even after all this i was still thinking 3550 but then i read something else. the 3550 is 2000 lumins. now i know lumins is not everything but bare with me. I found a good sourse for the image quality of the 51 and compared it to a great source for the 3550. The 3550 looks greta it does, and im sure it wont disapoint but it looks and feels like its less brighter than the 51 and it clearly has a grey tint to represent the darker image. Im thinking the lower lumins is posibly cause that differental. When i look at the uhd51 image yes its very bright in comparison but i feel it makes the colours pop more. Maybe the 23550 hdr will handle well and bring it up more but havent seen any footage to compare.
For me im only 9-10 feet away for projector and screen and im only after 92 inches cause its a small room but i feel the sharpness is something that will anoy me if its not there, more than going from good black to slightly better blacks. caus ethats what it feels like people are saying.
If you care about sharpness its uhd51 and if you want better blacks just, a smaller light border and hdr handled beter then benq.
Below is my dodgy projector and the image it gives me, about 75-80 inches. screen is 92. Its not bad for a tablet free bee lol. just anoying that i have to play the same movie on kodi, pc and on tablet on plex and cue up audi so i can have a 5.1 experience lol.