Yeah It does sound different haha. Basically the main differences are the engines are RR BR715s instead of the the P&W JT8Ds. Also the cockpit instruments and systems are the same as the MD-11s. The model differences are that the 717 has the DC-9 shaped wings (pretty much the same thing with a few minor differences  on the trailing-edge) And the MD-87 has the MD-80 shaped wings. Another difference is the MD-87 is 130' 5" and the 717 is 124' 0". The bottom line is that they're very similar but the 717 is more advanced.