Low end user here, so take my advice with a grain of salt.
I went with parallels because I wanted seamless integration with some programs that are only available in Windows. But every time I upgrade the OS, the parallels software says that I should upgrade it as well to stay compatible, costs money though.
From what I have read, you are better off with boot camp for games. Running Parallels on top of OS slows things down, not an issue for me as my Windows only software is not that demanding. With boot camp, you either boot up in Windows or OS, so your machine runs great, but only as one or the other. At least in Parallels both Windows an OS can be running at the same time, but slower.