The disk size Mac OS X Tiger powerpc iso file is 35.9GB. If you don't plan on storing data on this Mac OS X Tiger 10.4 installation DVD, the storage space is not a concern for the size difference.
PPC processors are a family of multiprocessing microprocessors developed by International Business Machines Corporation (IBM) for use in their PowerPC-based personal computers and workstations. These vendors include Apple Computer, Inc. with Apple PowerMac workstations and personal computers, Compaq, Digital Equipment Corporation (DEC), Fujitsu, Inc., and Hewlett-Packard.
These processors are known collectively as "POWER" and will be referred to as so here. PPC chipsets are the integrated circuits used in the PowerPC motherboard that provide the interface between the PowerPC processor and all other components of the personal computer system. The operating system and other software are responsible for accessing the PPC hardware.