Use regional managed instance groups and a global load balancer to increase performance because the regional managed instance group can grow instances in each region separately based on traffic.

Use a global load balancer with a set of virtual machines that forward the requests to a closer group of virtual machines managed by your operations team.

Use regional managed instance groups and a global load balancer to increase reliability by providing automatic failover between zones in different regions.

Use a global load balancer with a set of virtual machines that forward the requests to a closer group of virtual machines as part of a separate managed instance groups.