My two littles are only 15 months apart, but oh, what a difference there is between 3 and 4!
Here, Miss O is doing her best to cut little squares out for a pumpkin project we did this week. She loves to practice cutting, but is no where near being able to snip a straight line:
Now notice Little Bean's perfect little snipped squares. He has mastered the straight line, but has more trouble with cutting out a shape or cuting longer lines that require you to move the scissors forward more than once: