No you only need one that works. I prefer a name brand, but that is not a requirement. The main thing you need is one long enough to reach from the back of the PS3 to the back of an HDTV.
You don't the laptop HDMI is to connect to a HDTV and so is the PS3 HDMI. Even if you plugged both into the HDTV you would not get a connection between them. The laptop may also be able to connect...