Obviously, more surface area to hit with a tennis racquet. However, the best serves are faster than the best fastballs (some reaching >125 mph). Tennis players have more time as the court is 78' long (although the server always hits the ball inside the baseline, the returner is almost always several feet behind the baseline when they return the serve). Tennis players have to move both feet to get into position on almost every serve while baseball players don't. Both have an enormous amount of spin. The 'strike zone' for a tennis serve is much, much larger so the serve has more room to curve due to spin and still be a good serve. The best servers have perfected the ability to spin their serve both directions as well as hit a flat serve. No pitcher has both a curveball and a screwball so a baseball hitter knows a pitch, if it's going to break, is only going to break in one direction. Weather conditions would affect a tennis serve more as it's a lighter ball and it travels a greater distance.
Not sure which one I'd pick as harder, I just know I have no prayer of ever being able to hit either one.
Not sure which one I'd pick as harder, I just know I have no prayer of ever being able to hit either one.