There is no such table or field that I am aware of.
There are last updated date and updated by fields in the project and task tables, which I think relate to when something was saved, but they do not make a difference how to update was done.
If you think of it in Clarity you would perhaps edit a small number of fields at a time while when using a shceduler or doing schedule in the browser you might be saving a large number of edits within a small time frame say less than a minute. Though OWB might just save delta and not write everything back to the database. But again no differentiation between the schedulers or browser.
You could develop some analytics to see if there is a trend in the last updated fields of project data, but out of the box there is nothing.