Is there a difference between dragging a footage item onto the New Composition button in your Project panel, and directly dragging it to the timeline? I was told dragging directly to the timeline loses some of the data, but I've tried it and haven't noticed a difference.
These actions do different things.
Dragging a footage item to the New Composition button makes a new composition with features that match those of the footage item. The new composition contains a layer based on the footage item. See "Create a composition".
Dragging a footage item into the Timeline panel just creates a new layer in an existing composition. See "Create a layer from a footage item".
I'm referring to when you drag a footage item into an empty timeline window (when there is not already a composition created in the current project)