I have a smaller 'volume' foot, normal width and like a decent toe-box size like Keens. I wear a 42 in Sidi Ergo 2, 41 in Adidas and found I am BEST suited to a 41 in Shimano's 310 shoe. This after trying 42 and 41.5 sizes. The toe box is roomy, the thermoformed fit is nice. The cat-tongue heel gripper does work great. One thing is the tongue of the shoe is not long enough to cover where the shoe can dig in to the front of the ankle. If you are buying a pair, really tighten them up and see if they are going to bother you! My position compared to SIdi Ergo2 is Shimano is CLOSE, but needs a finite adjustment, like the dial mid-foot on the Sidi. Sidi's are also a bit more narrow in design than Shimano. I find as I ride and the shoe warms up/gets moist from sweat, that I can easily adjust the buckle and dial. I adjust a couple times before I get to my final 'locked-in' race ready setup. Sloppy shoes equals lost power, hot spots, and can be dangerous on knees and ankles with Repetitive Stress Syndrome. Sidi's replaceable heel bumper beats Shimano and is a bigger dimension too. Verdict - If you can get a DEAL on the Shimano's and they fit, go for it. If you must have the best of the best, Sidi is still top-dog.