The problem is [16]byte would always be wasting 12 bytes for IPv4 addresses if you only used one type for both. So, two types must be made which requires extra code and doesn't allow for == comparison which is what OP (GP? whomever...) was complaining about not being able to do since net.IP is []byte.

Sorry for the rhetorical device.

Isn't the indirection overhead of a []byte more expensive than a spare 12 inline bytes?

Yes, and a []byte is even going to have at least as much inline overhead: it stores 24 bytes (length, capacity, pointer), and of course plus the 4 bytes of actual data. Even on a 32-bit platform, the []byte inline storage is 12 bytes.

I think the point was that when it's a mere alias, you can end up passing an array of the right size and type that is not an IP address.