Yes the harder questions do count. If you check the Official ETS GRE guide it has two score cards that convert your raw score. The more questions you answer correctly in the first section, you are more likely to get on par, hard questions in the next section, ultimately when converting your raw score, even if you get, say, three questions wrong, you can still get 170 if the sections are harder.
If you don't answer your first section very well, you will probably get easier questions and even if you answer one question wrong, you cannot get 170. That's the difference.