MOSFETs with higher current rating often have a lower Rdson, that's a good thing (less losses when turned on), but they conversely are often slower and harder to drive (higher input capacitance/total gate charge and slower turn-on/off delay times), so you can't got crazy on the current rating because it'll be counterproductive: the MOSFET will be much less efficient when switching and the MOSFET driver will have a hard time driving it. Some MOSFETs (very often the low-side on synchronous buck converters) have a schottky-type body diode, that has a lower voltage drop than a "regular" body diode.