Many users find WiFi convenient (of course!). And it’s essential for iPhone and iPad and many televisions (streaming), etc.
But for computers, MPG strongly recommends gigabit ethernet instead of WiFi. WiFi at its best is inferior to gigabit ethernet, flaky from various types of interference, less secure, and comes with high latency that results in (for example) excruciatingly slow file copies, particularly for many small files.
Mark A writes:
Under Mavericks, I had ethernet priority over WiFi and Yosemite reset it without warning to favor WiFi.
So I was experiencing issues while the cable was plugged in and took me a while to realize the traffic wasn't wired as I'd set it and I didn't think to double check after an O/S upgrade.
MPG: Mark is correct, which I have confirmed by turning on WiFi, observing poor speeds rebooting, and continuing to observe poor speeds: WiFi is taking precedence over gigabit ethernet; it’s about 10X slower to load a graphics-intensive web page.
Tip: change the precedence of networking items by dragging them to set the order. (WiFi inexplicably defaults to being first before ethernet, a bug). Drag ethernet so it is at the top of the list, then WiFi can be left on and harmless when connected to ethernet, yet be active when not.