Powerline is the way to go. Faster and cheaper. Yes it is cheaper. A set can be found for $50 on sale at any retailer at any time. Wifi is garbage unless you have a good wifi card/dongle and a good wifi router. Both of which cost at least as much as a Powerline Ethernet Adapter set on sale.
The only issue with Powerline Ethernet that you may encounter is when using them power bars/surge protectors. Although personally this doesn't affect my set I have heard it can severally hurt ping and speed when used on certain bars. I use a belkin power bar. Nothing special but not one of their cheaper ones either.
I highly recommend powerline eithernet for many reasons, cost, speed and ease of installation to sum it up.