I would recommend powerline over wireless, its (usually) will have less interference from the environment/other devices. Also depending on the type of powerline adapter you can get a higher bandwidth connection for your internal network.
When you are transferring files between computers, a wired connection will also usually outperform wireless connections especially on multiply smaller files.
It really depends on your use case. If you are just using the internet and maybe the odd file transfer a month go wifi and don't worry about spending the money. If you do a lot of file transfers between computers on your network. You will probably benefit more from a wire connection.
That being said, ensure that your router and computer are connected to the same power circuit in your house, otherwise a powerline adapter will not work.