I like the serial way of port expansion with shift registers (74HC595 outputs / 74HC165 inputs).


Its also the less expensive solution, since you can place any shift register directly on the place where the I/Os are needed and use only a 5 wire bus to connect them all.
So you can made a cheap one-layer pcb.


The high expensive solution use a bad solderable high costly high pin count BGA part and an expensive six-layer pcb to distribute the tons of I/Os all over the pcb.


Peter