Hills. You can plan for them. A hill has never moved me dangerously close to traffic, nor to the shoulder without warning. A sustained gust of wind brings no forewarning, thus no ability to downshift in advance. As noted, wind gets you psychologically. Going 10 mph up a hill makes sense, going 15 across a flat is maddening. If you're going the "wrong" direction into the wind, you don't get rewarded for the extra effort, the punishment just continues on and on and on.