GeeJayVee,
I have hundreds of 3CX installs under my belt so I think I can share with you some real-world experience.
3CX works well on both Windows and Linux. For example, I have customers who have been running 3CX reliably on Windows for years with up to 1,500 extensions on a single 3CX instance. However, the Windows version of 3CX, without question, needs more resources than it does running on Linux (RAM/CPU). As a result, if you plan on hosting 3CX it is far cheaper to host 3CX on Linux. Personally, since I'm reasonably proficient with both Windows and Linux, so I tend to go with Linux simply because of cost.
We could jump into the debate of whether Windows or Linux is more "reliable", but let's just leave it at both platforms can be very reliable if the OS is properly implemented and maintained on reliable infrastructure. Personally, I'm agnostic. Either choice is valid depending on the situation.
For most implementations, you really don't need to get very involved with Linux administration. Frankly, if you get into trouble with your Linux server, it is easy enough (and pretty fast) to just reinstall everything from scratch and restore your 3CX configuration from backup. Naturally, the more you know about administering Linux the better, but you don't have to be a Linux guru to run 3CX on Linux.
A reasonable person might assume 3CX is more reliable running on Windows because 3CX has many more years running on the Windows platform, right? But 3CX is written in .Net Core, so the base code is identical for both platforms. As a developer myself, in my experience, the .Net Core code differences between Windows and Linux are trivial. So it is no surprise to me that 3CX was very stable on Linux right away.
Regarding 3rd-party applications, all our VoIPTools add-ons equally support 3CX running on Linux or Windows so I don't think that is a big consideration anymore. Keep in mind that 3CX Support doesn't want any non-3CX software running on your 3CX server, so any 3rd-party tools should be installed on a separate server anyway. Provided the add-on can talk to 3CX from a separate server, it shouldn't matter what OS (Windows or Linux) 3CX is running on.
My advice to you depends on a couple of factors. For example, if you plan to host on-prem and you have sufficient hardware, by all means, feel free to install 3CX on Windows. On the other hand, if you plan to host 3CX in the cloud, and cost is a concern, any reasonably intelligent person can handle the demands of administering 3CX running on Linux.
UPDATE:
Last I checked, running 3CX on Raspberry Pi is no longer supported.