Get fitted, and don't follow any advice except what fits. I'm 5'-9" tall, but ride a 58. Why? I have long legs, 34" inseam. So I have a Trek Madone 5.2 "H3" fit, which lifts he head a bit. And I needed a shorter stem to prevent excessive reach. But it works. I've ridden it thousands of miles and still love it. So just get what fits.