T&C brake pad replacement?

Have a '03 T&C that is about due for new front pads. Will be replacing them with ceramics in an effort to get rid of the 'black crud' from OEM's. Have seen the ceramics from $100 at NAPA to as low as $44 at Pep Boys. What is the huge difference in these pads ? Also, two sizes are listed at Pep Boys. Can I determine which pads to purchase without actually taking off the old ones first ? Have disks all the way around, but this didn't seem to be enough info. Thanks ! Zork