Usually with wireless keyboards and mice these days they don't have that noticeable of a lag, but they do suck up batteries like their nothing. If your going to be playing a game where reaction and time is key like in an FPS you don't want to worry about something like your batteries dieing on you mid game, and if your really hardcore about things like your aiming and shooting need to be SPOT on, then that slight lag will drive you crazy.
I prefer wired. Wireless is such a pain in the ass. I normally just buy a cheap 12 dollar keyboard because i replace these at least once a year. I bought the logitech g550 laser mouse which is awesome. All wired. I hate having to worry about batteries.
Razor is great but the mouse life span is poop. They are super precise however, I have not had a razor which didn't need replacing sooner then I would like. But if your a lefty like myself you are stuck with more limited options. Otherwise get a Logitech MX 518 which is the best on the market.
Yeah, I heard that the MX 518 is an amazing mouse. It looks pretty good as well.
Thanks for your input guys, it seems wired is the way to go; more specifically, the Razer Arctosa silver and the MX 518.