I would like input on anyone who has run both of these machines. I understand the 9500 has a larger engine displacement. I just wasn't sure if there were different "efficiency" changes made. The 7720 I currently run is a '84. The 9500 I am looking at is a '91 model. I don't think it makes too much of a difference but I ran a 920 on the 7720. Will be running a 922 on the 9500. Thanks in advance.