I'm having a hard time finding information about whether implementing ipv6 or using a stretched vlan is a better option for geographically dispersed sites is better. Does anyone know:

1. Problems with stretched vlans (mac address broadcasting etc)
2. costs for devices to solve those problems
3. pros for using IPv6 instead

EDIT. What I am looking for is pros and cons against implementing the equipment required to implement stretched IPv4 vlans vs simply using IPv6 to solve the same problems. Eg admins stretch vlans instead of route because protocol X can't be routed, but IPv6 can encapsulate protocol X so there is no need to worry about that problem.