As far as speed goes, Black > Blue > Green. You do NOT want a Green drive as your OS drive, or one with a pagefile on it; they're fine as data drives but are obviously slow as primary drives. The speed advantage of Black over Blue is less pronounced, and is at the expense of noise; my WD Black is one of the loudest drives I've owned. It's fast, and works very well, it's just noisy. It is also a little warmer, but that hasn't been a problem. With the prices you list, I'd think the Blue drives are obviously the better deal.