Hi! So I'm a little confused by what seems to be a contradiction between what you've said in another video and what is sai...

You are right, according to the circumstances you'll prefer rotating in Object or Edit mode : When you enter Edit mode, all what you do to the object is change it's mesh data. So the transforms that you do, apply to the verticies, edges and faces that creates your object. However you are in Object mode, you are no more working on the objects MESH data but on the objects data itself ! So that's when you change it's local space. Now imagine you've just added a cone in your scene : (By default it's local space is the same as global space) If you enter Edit mode and rotate it 45° for the tip to point on a diagonal and then go back to object mode... What you've done is just Edit the mesh of the object as if you wanted to say : "by default I want my cone to be rotated 45°". At this point, what you have in front of you is the same as if you had done "Shift+A" > add mesh > and lets imagine that in the list of primitives you could chose a 45° rotated cone. But the local and global axis of your object havn't changed at all, Blender considers that the Z axis of your cone is the same as the global Z axis... It just doesn't pass through the tip of your cone anymore because the shape of your cone has change (you've changed it to say that the shape of your cone is "a cone rotated 45°") Now, lets say that you never entered Edit mode and instead, you've rotated your cone the same way but in Object mode... This time, you are not changing the shape anymore, you consider your object as a block and all the changes that you'll do to it will be done to the objects data directilly. So by rotating it, this time, you rotate the local space to. Hope all this clears it out for you ^^'

Thank you.

Welcome. :)