官方：
Transform.Find
public Transform Find(string n);
Parameters
| n | Name of child to be found. |
Returns
Transform The returned child transform or null if no child is found.
Description
Finds a child by n and returns it.
If no child with n can be found, null is returned. If n contains a '/' character it will access the Transform in the hierarchy like a path name.
Note: Find does not perform a recursive descend down a Transform hierarchy.
GameObject.Find
public static GameObject Find(string name);
Description
Finds a GameObject by name and returns it.
This function only returns active GameObjects. If no GameObject with name can be found, null is returned. If name contains a '/' character, it traverses the hierarchy like a path name.
For performance reasons, it is recommended to not use this function every frame. Instead, cache the result in a member variable at startup. or use GameObject.FindWithTag.
Note: If you wish to find a child GameObject, it is often easier to use Transform.Find.
Note: If the game is running with multiple scenes then Find will search in all of them.
通俗一点的理解：
Transform.Find是查找当前对象的子物体，即使子物体的active = false，也能查找到（当然当前对象必须active = true），效率更高。
GameObject.Find是查找整个视图中相对应的资源，如果需要查找的物体的active = false 或者要查找的物体的父物体任意一个active = false都不能查找到。另外，该方法不能放在Update里执行，因为太耗费性能。