For the PC; chair. Always the chair. I hate trying to type when lying down, and couches are just weird for using a computer. You get too low, or you can't sit properly when typing, and it just gets annoying. For consoles, either chair or couches are allright, but not lying down. Lying down just feels very unnatural and too relaxing, and just sorta counters that alertness and the adrenaline you get from gaming.