The key differences are:
CSPPC memory controller is 64-bit and requires memory installed in pairs.
BPPC memory controller is 32-bit and memory can be mixed and matched.
CSPPC memory access is considerably faster due to it being 64-bit vs 32-bit.
BPPC can have 256MB ram VS 128MB on CSPPC.
Other key differences that should be mentioned:
CSPPC SCSI controller is UW-SCSI3 (40MB/s theoretical maximum speed)
BPPC SCSI controller is Fast SCSI2 (10MB/s theoretical maximum speed)
CSPPC has a 604e PPC cpu VS 603e on BPPC.
