Mostly this makes no sense because the things BGP cares about are orthogonal to mere IPv4 or IPv6 addressing.

But if there is a difference, IPv6 means less prefixes are needed for any given provider, since the IPv6 prefixes are huge and unfragmented, we can usually give a provider enough address space in their initial allocation to last them forever, and if they exceptionally out-grow it, the larger space is available, whereas with IPv4 there's no chance anybody can give you a /16 even if you warrant one.

It means less prefixes until people start announcing each /48 in their /32 separately...

Oh yeah, nothing makes a mess of your network like someone coming in and saying "we need to remove these IPs from the middle of our advertised blocks for security reasons".

I think we're going to see less of this due to IPv6's design, renumbering is less of a pain than it was with IPv4 so instead of splitting off a route in the middle of your address space and bloating the BGP table you can just move to a different subnet entirely.

Network Operators dislike buying new hardware. As the policies matriculate through tiers of providers, raw numbers of announced prefixes becomes a sticking point.

BGP works fine for IPv6. This is not a good reason.