I would disagree with that assessment. There are many new 8051 based processor chips in current use, I have two products in use now that use the 8051. But by far my processor of choice is the AVR (about 27 products, and 4 with the PIC). A lot would depend on how large a system you need. For just RFID and a load cell, I would recommend the PIC (actually, I would recommend AVR, but that wasn't one of your choices). For a larger system that might include more sensors or user interface, I would go with the 8051.