The Epson 4000 is an interesting case study. Especially since its new p r i c e putting it head to head with the HT3550. I'm on record having replaced it with the HT2550 and being happy with what I feel was, at the time, more or less a lateral move. I was reviewing the HT2550 and was planning on putting the Epson 4000 back up as my primary driver, but some strengths the HT2550 has over it led me to send the Epson back.
The 4000 is just stupid easy placement flexibility. Epson is known for that but add in motorized zoom, focus, and shift... and it's crazy how easy it is. However, that benefit was easy to look past since that ease of setup only affects the initial setup and my space did not require and need for extra vertical/horizontal shift. The offset and throw of the HT2550 were already perfect for my theater. So for me that was a wash and no reason for me to choose one or the other, although a lot of people might need the extra placement flexibility.
The 4000 has pretty average blacks. That's the main difference between it and its older brother the 5040UB. The downgraded panels in the 4000 gave it a lower price tag and lower black levels. That was the only material difference. I'm on record acknowledging the 4000 had better blacks than the HT2550.
^^ Those are the two main advantages that I saw between the two. Color brightness was also better on the 4000 but not by much to my untrained eye.
There are a few reasons reason I stuck with the HT2550 even with its less-than-fresh contrast.
1 - with my 160" screen I noticed the difference in resolution. The 4000 is a 1080x2 shifter for 4M pixels. The HT2550 has 8M distinct on screen pixels. My untrained eye noticed that.
2 - Color and delta-E looked better to me on the HT2550
3 - The HDR implementation on the HT2550 was handled better
4 - I couldn't stomach investing in a projector that had a 10.2gbps HDMI chipset. HDMI 1.4 was released in 2009 and it is STILL being used even by the 4000's successor, the 4010???
5 - This is something I could have lived with but look at the size of the 4000 compared to the HT2550. The projector is one of the first things that people see when they come into my theater. The size of the 4000 was legitimately obstructing the view and made the HT2550 look like a pico projector.
^ That comparison was with the HT2550. So I would not declare the HT2550 the winner in that fight. It was the winner for me, but the Epson4000 is still a very good projector. You just need to know the tradeoff and make the decision that makes sense for you.
When comparing the HT3550 to the Epson 4000 on the other hand, I think after trading blows the HT3550 is the objective winner with a few bit of context below.
1 - Placement flexibility is still better on the 4000. Not impactful for me but the fight could stop there for those who need that flexibility. However, the shorter throw of the HT3550, in my opinion will probably give greater flexibility to a broader target audience so that's a wash still.
2 - Native contrast might be better but I can say that in normal 'best settings for all viewing cricumstances', the HT3550 bests the 4000 in contrast and black levels.
3 - The HDR implementation lead of the HT3550 is even wider than before with the HT2550
4 - 18gbps
5 - Color accuracy
6 - Styling and size (subjective)
7 - input lag nod goes to 4000 (35ms vs 55ms)
8 - Color brightness when calibrated slightly better on 4000.
9 - 4M pixels vs 8M pixels. I notice the resolution.
So that's my take on it. I pick the HT3550 head to head with the Epson 4000 10 times out of 10 for most setups.
The HT3550 vs Epson 4010 is honestly a more interesting battle since the 4010 ups its game with color accuracy and blacks. However, hardware-wise it still touts the 10.2gbps chipset (heaven knows why) and is still 4M pixels. I think the HT3550 vs 4010 battle is very similar to the HT2550 vs 4000 battle... but the 4010 MSRP is five hundred more than the HT3550. I haven't had hands on time with the 4010 so I can't tell you which is better. However, after the projector trades objective blows, the buyer has to decide if that price difference is worth it.