Well, here are my thoughts on the matter:
 * ipaddr is relatively small, fast, and focuses on some core functionality
 * netaddr is designed to be very flexible (sometimes at the cost of a
little speed), leaning more towards a network calculation/address
manipulation "framework"

As such, and given the recent work made to ipaddr to make it
stdlib-friendly, my vote would be to include ipaddr in Python while
netaddr can continue growing, providing its user base with diverse
functionality while hopefully taking advantage of ipaddr in the Python
stdlib as much as is practical and useful.