Along those lines - I know now that IPv6 determines default gateway via router advertisements - but what happens if there's two or more routers on a LAN, that could all get to my destination, but some more efficiently than others?
Another scenario is in a shared environment like a lab, some IT folk will send their traffic to one router, and another to another router for X reason....is this functionality just part of the beast that is stateless autoconfiguration, and if I want something more controlled I should use something like DHCPv6? (I hate that I just turned this into a yes or no question - elaborate if you can

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well IPv6 RA has a provision for a router preference. RFC 4191 describes this.
From my understanding, per-destination preferred routing is not possible via RAs, but globally a router can be defined as more preferrable for hosts to utilize.