
Google Cloud has 2 type of Network Tiers. Premium Tier and Standard Tier. Maybe you want to ask, who is better between of both tiers. With see the naming convention we are know the premium is better than standard tier. Let's see the difference between both of them.
Premium Tiers deliver over Google Network. With this network, the premium tiers well-provisioned, low latency, and highly reliable with global network. This network has over 100 Network POP closed with end-user ISP arounds the world.

Standard Tier is new feature with offering for lower cost. This network tier provide network quality comparable with others public cloud provider but lower than Premium Tier by GCP provider.

Standard tier has complex traffic because the traffic not deliver through Google network but ISP network.
I have created 2 instances with same specification but different network tier.
The vm-premium has minimum response time in 114ms and vm-standard has minimum response time 142ms. This ping test proof the premium network tier has better response time than standard network tier.
Note: The result of this test may be different because the network traffic is dynamic and the result may be different in each test.
Medium Post: Who is better? Premium Tier or Standard Tier on Network Tiers Google Cloud