Debugging a binary that you don't have source to, and that you don't intend to modify the reduces the benefit of the full IDE (where your syntax view in debugging is the same as your editor). Still, you get all the niceties of the IDE. You break on a line, step further on some lines. Notice the bug happen after y = foo() + bar(). So you wonder "where are those?" and you F12 with the cursor on the method name to nav to that method once there you set a breakpoint on the first line, and run so you debug that next.

Also, if you add in edit-and-continue so you can modify the code and have it automatically recompiled and keep debugging it, that adds value too.

I assume that various editor adaptations for vim/emacs etc means that you get almost all the IDE experience with gdb as well (symbol navigation, syntax highlight etc) and at that point there is of course little difference between one IDE and another.