There are some marinas with boat slips laid out cross to the prevalent breeze. Avoid them: They will always cause headaches and the leward side of your boat will constantly be scuffed and marked from rubbing. The vast majority of marinas, fortunately, are smarter than this and have their slips pointing into and away from the wind.
Because sailboats have relatively small and ineffective propellers, particularly in reverse, they need the breeze in front to stop easily at all. Similarly, their poor performance in reverse makes backing into the wind very difficult, if not impossible. Also, because sailboats’ sterns are U-shaped, their prop walk problems are enhanced, so backing into a slip is inadvisable. Therefore, sailboats need to be on the downwind side of the dock, where the breeze helps them leave and stop, when entering their slips.
Powerboats have a different set of challenges: Their engines give great mobility and control at their sterns but their light bows are highly vulnerable to being pushed around by a stiff breeze and it’s often impossible to point a powerboat into a strong wind, in harbor. Doing this in a crowded marina, particularly with average boating skills, is one of the most common causes of boat crashes at dock. Backing powerboats into slips is at least as problematic and fortunately, few recreational boaters attempt this (For those truly skilled and comfortable backing into a slip in a stiff breeze, who like their boats docked that way, the downwind side is appropriate for them.). Safe docking for powerboats in a breeze mandates their being upwind of their slip and letting their bow drop into the slip. It’s easy for a powerboat to stop their motion, so a slip on the upwind side of a dock is perfect for a powerboat.
It’s a Yin and Yang thing. Neat, eh?