I use tree style tabs and typically have anywhere from 20 to hundreds of tabs open. My workflow is basically opening anything I find interesting for further review which naturally opens in a tree so the main task grouped together. I use them as soft bookmarks to come back to where I am, generally closing the sub tabs when I'm done with them or closing the whole tree if I'm done with the main topic.

I use bookmarks for infrequently used items that I know I will come back to at some point, the tab groups are more transient.