Essentially the best thing you can do is try it over both wired and wireless and see how you get on. It is near impossible to predict the sort of speeds you'll get over wireless due to how much the performance can be affected by your router, wireless adaptor in your PC as well as nearby devices and the layout/construction of your house. It would just be a simple case of connecting it with a cable, running a speedtest then running it over WiFi and running a speedtest again, see if the speed is massively affected.
For me, if it's a desktop and it's even slightly convenient to run a cable to it, I'll connect it with a cable.