I found this Can an NS Record Point To Multiple A Records?, but wonders what is the difference, if any.
mydomain.com. IN NS ns1.myhost.com. mydomain.com. IN NS ns2.myhost.com. ns1.myhost.com. IN A 111.222.333.1 ns2.myhost.com. IN A 111.222.333.2
mydomain.com. IN NS ns.myhost.com. ns.myhost.com. IN A 111.222.333.1 ns.myhost.com. IN A 111.222.333.2
EDIT: actually, come to think of it, it could be said the same for MX records. Any breaking differences?
EDIT 2: then again, MX allow use of priority values so its a different case, in that one-ip-per-domain is more useful sometimes.