lucy24 - 11:12 pm on Feb 3, 2013 (gmt 0)
In a word: everything.
This is not literally true-- logs don't show complete headers, for example-- but close enough.
But why are you asking us? Why don't you look at your own logs and see for yourself? Compare the content of full logs to what you see in (1) generic analog stats (the kind provided by your average host) or (2) the analytics program of your choice (human visitors plus those members of the robotic elite* that you haven't excluded by name).
* For a given definition of "elite", duh ;)