Using WiFi does introduce a bigger attack surface: an attacker can try to exploit problems with the network without physical access to a network access point (e.g. an Ethernet port).
This generally allows for longer running attacks without being detected.
The security measures put in place for WiFi are (given they are configured properly) acceptable for now, but this might change any time in the future without being able to be detected right away.
There are additional minor concerns about network segmentation (which is more costly to achieve using WiFi) especially for businesses.
The general rule of thumb should be to use Ethernet with its easier (physical) access control where this is possible.
Often times, WiFi is needed in order to work with mobile devices today. If that is the case, make sure to be informed about any new vulnerabilities regarding your WiFi setup.
As to the operating system: supposed to have an arbitrary amount of time and motivation, the operating system is of no concern in either direction; all complex software is very probable to contain some unpublished, unfixed vulnerability that can be exploited.