I have 2 MAX UV and one 4K Pro. MAX printers are problem free and accurate from the day one. I have had a lot of problems with 4K. It is currently coming back from ASIGA. The main problem was that printed dies were too big.... same files printed with MAX were perfect. I made numerous tests etc and eventually had to send the printer out. In ASIGA there are people, who are a bit how to say... stupid? I described the problem with the dies 10+ times. And eventually I got a question that ruled them all... If the coping/crowns do not fit on the dies, does it mean the dies are too big?.... Wow, what a question. I sent them a picture as it is impossible to describe something so simple again. After the picture I got a genius answer. The printer prints the dies a bit larger so maybe this is you problem.... Again, no words. I am using -ini files from the homepage and these are working with MAX printers. Obviously there is someting wrong either with the 4K or the -ini file. And the final conclusion - there is someting wrong with the -ini file and they dialed the parameters in. I am currently waiting for the printer to see, if the problem is really solved. As I used the 4K alot for waxups, I can say that with 25 micron, it seems MAX and 4K both have quite similar outcome. 4K projector is needed for the larger build area to have the pixel size small.
If you are printing many things besides models, then having only one 4K is not good. 4K is meant for mass production of models. It is quite stupid to print small gingivas etc on a large printer that needs to have basically the whole bottle of material inserted in to the resin tray. I print splints, operation guides, try-ins and shell crowns definitelly with MAX and models, waxups and custom trays with 4K. When the operation splint amount rise, then I switch to 4K. For now I did everything with 2 MAX-es and it is definitelly better, than having only one 4K. Custom trays I have done with Phrozen Mighty 4K as it is enough for that. But I would never use it for anything else as ASIGA overall is many times better in everything.
At the end of the day it comes down to the number of units printed. Currently it is enough for me to print with 2 MAX-es + 1 4K but as printing increases every month, I might need another 4K soon.