I have to disagree with the above a bit. I hate running cables over long distances as a clean install takes a lot of work especially if doors are involved. As a result, I have been using wifi in my current apartment. My SpeedTest is 5ms ping, 33.53Mbps DL and 18.49Mbps upload with other devices using the wifi too (5 devices total, though iPad and AppleTV are usually sleeping). This speed has still worked fine for streaming and playing, so even if a wired connection is marginally faster and "more solid", wireless works fine as long as you have a quality router and a good ISP.
That said, as you have a long distance from your modem, you would probably have to use a booster between the wireless router and the computer to get a good signal, which makes the wired route a smarter choice.
As long as it's an 802.11n card, he shouldn't need a booster. However, you do make some good points. SOME people don't have that problem when using wifi. If he has a problem with wires going all over the place, then he should get a wifi card. Just know that interferences can occur when using wifi over ethernet. Not saying that it'll happen to him, but dropped signals, higher latencies, and lowered speeds can occur because of the layout of your home, objects blocking the signal, interference from electrical devices or
your neighbor's wifi networks, etc. If you have a high quality router and a good ISP, yeah he shouldn't have any problems. But if he ever has a problem with how slow his internet may be at the time or why he's getting dropped frames (if he ever does), the question will lead back to "Is your internet hard wired to your router"? You have a damn good ISP from the sound of it, which I am jelly of lol. My ISP is currently CenturyLink and my DL speed is 25MBPs to whereas my UL speed is 1.5 to 2MBPs.
The only way he'll know is by trying out the wifi card. If he wants to see if anything like that occurs, he can find out really quick with the wifi card. If he doesn't experience problems with the wifi card, then great. But if he does have problems with it, he'll have to make the necessary upgrades (like getting a new modem, going hard wired, changing ISP's, etc).