What is new. The logo required properties use to just say it accepted the URL property, but now it says both URL or ImageObject. Here is a screenshot of this section of the help document:

ImageObject type gives you the ability to add additional data to an image, such as width and height, or the author or a caption. Whereas the URL type did not give you these added values.

Why we care. Google is giving us a bit more flexibility with implementing logo schema and structured data going forward. So if you are using these schema, you may decide that going forward that you want to use ImageObject type over URL type – or not.