On networks using NAT64 (and maybe also for DS-Lite, although I'm not so sure there), the IPv6 path is more direct than the IPv4 one since it doesn't need to go through a CG-NAT, which might be at capacity (tracking every TCP connection requires memory) or located farther away than the nearest IPv6 egress router, making routing more indirect.

I believe all three large US mobile carriers use NAT64 at this point exclusively, and CG-NAT is quite common in DOCSIS cable networks.