Cons of ROM-port-hardness (vs. scrypt)

Good scalability of attacks to more computing power (CPUs, CPU cores, GPUs, etc.) while not having to provide more memory
However, if the defender stayed just below saturating the memory bandwidth then the attacker may have to provide more bandwidth first
A custom or otherwise more suitable hardware setup would have a larger number of ports to the same ROM capacity
Moreover, those don't have to be ports to the same large ROM - instead, separate smaller ROM banks may be used as long as bank conflicts are fairly rare
Yet at below ~1000 cores sharing a ROM the attack speed per die area will be lower than for scrypt, whereas with more cores the attacker will have to provide more interconnect and ROM ports, which will have a cost of its own