Apples and oranges.
The $200 Amazon special will probably work. Well, what you have works. This is for “works better.”
There’s nothing really wrong with most of these printers, and there is certainly a diminishing returns element. It costs a lot more to get a little better generally.
My Repeat compares well to some failrly high end stuff. I haven’t the really expensive printers, but I’ve seen them at work.
Some of the advantages to the MP3DP v3 or v4:
True bed levelling. This is ONLY available with independent Z motor control, and requires 3 channels. Two motor bed levelling also exists, and is actually pretty good though.
CoreXY motion. This has less moving mass than most Cartesian designs where one motor exclusively deals with each of the X and Y axes. This allows faster printing with fewer artifacts appearing in the resulting print. Less printing time also reduces the probability of other problems like warping or clogging nozzles.
This is harder to answer. Apples to oranges again, I guess.
In similar configurations, you could look at a Railcore (Google says $1700 USD) or a Voron ($1350 USD) with options that can bring those over $2000 easily. Are those similar quality? My printing results versus what I see people who have those would say it’s in a similar class, but there are thinks to take into account. Can I get that result at the same speed they can? I don’t know.
Or you can look at a genuine Prusa MK3S+ for $1100. This is the same general configuration as your Ender 3, and while you can probably get the same performance from yours, chances are, you won’t.
With the MP3DP the quality of components is up to you. I have an E3D Hemera extruder for both my v3 and v4. That’s a pretty good unit, at a cost approaching the whole cheap Amazon printer kit, but I’ve used many cheap extruders, and this is worth it to me. My self designed printer uses E3D V6 clone parts, and gets satisfactory performance, but at a loss of Z height relative to the Hemera, and is much more picky to load filament into. Probably a difference of about $60 or so. My printer was designed around this, so I couldn’t change to the Hemera on it. On the Repeat, it would cost me about 40mm of Z height to use the clone parts.
Since this is not a kit, you will end up paying more for parts than the exact same ones that did come in a kit, but you pick and choose the parts.
I very much like having a 300mm print bed. This basically requires increasing the rail lengths.for X and Y by 100mm from the base Fusion360 model. That said, it is very rare that I actually use all of that real estate, and I am still using power to heat it all. This is one reason why my V4 is smaller. (I actually wanted to build it for 200mm.)
You will probably spend more for this than if you picked up, say a CR10 kit. (Just looked it up and for $390 CAD I can get a CR10 kit (300x300x400mm build volume) which is about the cost of my extruder and control board.)
It’s not like I couldn’t make the CR10 work. If I just wanted a functional 3D printer, that is a pretty good deal.