Also coming from a coolermaster case, the Mastercase Pro 3 will note positives and negatives and make some comparisons.
Positives:
*First of all, we are talking about a very large and imposing case, it is beautiful no matter where you look at it. Huge 200mm ARGB fans in the front for good airflow and the option to choose between glass or mesh cover for better airflow. (Both are included in the package).
*Built-in vertical GPU mount, which costs about 50€ to buy.
*Adjustable GPU support bracket to prevent sagging.
*4 glass panels included in the package.
*Many positions for HDDs/SSDs with the ability to hide them at the back of the case.
*Very good airflow with the mesh cover in the front, although it lacks a bit in the top due to the glass.
*Spacious with plenty of options for cable management with detachable metal covers and a door to hide every cable, making the system look clean from the side glass.
*USB 3.1 Type-C in the front and many other USB ports.

Negatives:
*I find it unacceptable that the website advertises that it can fit a 280mm radiator on the top, but it doesn't fit unless you apply a lot of pressure or remove the metal piece that hides the cables. So, if you install the radiator, it will look messy with a bunch of cables sticking out in the build. Also, a 280mm radiator fits on the front of the case, but not in a push-pull configuration unless you remove the same piece mentioned above. To give you an idea of the size of the radiator I'm talking about, my cooler is the NZXT Kraken X62. It fit in the Mastercase Pro 3, which was smaller, but it doesn't fit in this beast. However, I have a reservation because it may be a mistake from NZXT and the X62 radiator might be too wide, and other radiators may not have a problem.
*The side glass panels don't have a latch like in the previous Mastercase models. Now they have a screw that requires a straight screwdriver. Coolermaster doesn't provide a screwdriver like they did with the older models, so you have to find a screwdriver with the right thickness to install/remove them, and if the screwdriver is not thick enough to fit perfectly, the screws are likely to get scratched.
*The front dust filter is not easily removable for cleaning like in most cases. You have to remove the entire front cover and then unscrew the filter.

The system I have inside the case:
Mobo: Asrock Z370 Extreme 4
CPU: i5 8600k
GPU: Gtx 1070 ti rog strix
PSU: Corsair TX550M gold
Cooler: NZXT Kraken X62
RAM: Teamgroup Nighthawk RGB 16GB

Conclusion:
Overall, it is a beast of a case that is worth its money, it offers many features that other cases in this price range don't have, and it looks beautiful. Compared to the H500P Mesh, this one is clearly better and more cost-effective.
For an additional 40€, it offers 4 glass panels on all sides, GPU support bracket, vertical GPU mount, and RGB fans with ONLY 40€ more. The difference is minimal considering that just for a vertical mount, you would spend 40-50€.
Regarding the observations I made above, I consider them insignificant compared to what this case offers.
I highly recommend it without any reservations. It is fantastic in all aspects.