prelude: I wont get into the whole moral dilemma of if you should buy a clone vs OEM, as that frankly, is up to you, and I don't think people should be telling others how to spend their money.
Abstract: FYSETC make ok products, some stuff they do better (in my opinion) such as the integrated screens, and others they do okay with like the logic boards. They are not to the same high standard as Duet is, however functionally, they are able to provide the same experience, and have been reliable in doing so.
Quality: The main difference when it comes to FYSETC parts vs Duet other than the substituted components (probably due to local supply differences) is that the FYSETC duets tend to be a bit weaker overall. They are more susceptible to EMI and as such the webOS tends to get negatively affected more often than a true Duet would.
Accelerometer support also backs up this as the official duets can cope will full speed data capture, however the FYSETC needs to be turned down to half speed in order for an uncorrupted data stream. This is still more than acceptable resolution, however it does show some of the differences caused by the design differences
Wire interferences is also slightly more noticeable with the FYSETC boards. For reference, I use a 7" PanelDue and a 7" FYSETC integrated panel across multiple machines. Both have the same behaviour independently. However, with the FYSETC Duet boards, the screens are more suseptable to the EMI the machine produces, and it has shown up a couple of times, where the data lines suddenly produce garbled commands, which show up on the screens as bad json commands.
With that being said, both official Duet boards, and FYSETC share this issue, however FYSETC appear to have a interference rate 5x higher than that of the official Duet boards.
- This issue can be fully solved by using the new firmware that uses checksums
Its kind of sad to say, but FYSETC make a much nicer touch screen. They have integrated the breakout board into their screens, and overall has made the PCB footprint smaller. You do loose the speaker for this, however for that size reduction, I have to admit that I prefer the FYSETC 7i screens, and they also support all the new PanelDue firmware.
This is the only major difference I have seen between official Duet products and the FYSETC clones. When updating the firmware to new versions, the FYSETC boards don't tend to consistently update. The boards will download the files fine, and install them, however the firmware will not update after that - almost like it backdated the version to the one already present on the board. This isn't a massive issue as you can just upload it manually instead of through the WebOS, but it is a noticeable difference, as official Duet boards only rarely have this issue.
FYSETC is fully functional as a board manufacturer, even if the quality is slightly lacking, the products do tend to work fit for purpose.
They make some really nice screens, and their logicboards - while not 100% clones - do act like official duets, except for some behaviour changes, where I think the corners have been cut for cost, means they are more susceptible to EMI/EMF.