TLDR;
LoadBalancer most of the time,
ClusterIP when you want to expose your service internally,
NodePort for testing and development or batch purpose.
What is a service ?
Pods get assigned an internal IP adress at their creation. Client within the cluster can reach the pod on their internal IP adress.
But pods are ephemeral: An unhealty pod with certain IP adress might be replaced by a pod with a different IP address. The internal IP address isn’t a reliable option
That’s the issue a service attend to resolve: provide a reliable address to reach pods.
ClusterIP
ClusterIP type is the default type. It exposes the service on a cluster-internal IP. Only client within the cluster are able to access this service. Clients outside of the cluster cannot reach it, which can be desirable for security purpose.
LoadBalancer
This type of service exposes the application to external traffic through a load balancer provided by the cloud provider.
It’s the most used service overall. This is a more advanced and scalable way to expose an application, as it provides load balancing and high availability, but it may require additional configuration and resources.
NodePort
NodePort exposes the Service on each Node’s IP at a static port. It is the most primitive way to get external traffic directly to your service. This is a simple and straightforward way to expose an application, but it does not provide load balancing or high availability.
ExternalName
ExternalName map a Service to a DNS name.
This allows to consider an external ressource as an internal one, and appreciate Kubernetes built in ressource mapping using selectors and tags.
Conclusion
Overall, the best service type for you will depend on your specific needs and requirements. If you need to expose an application to external traffic and you do not need advanced features like load balancing or high availability, then a NodePort service may be sufficient.
If you need more advanced features, then a LoadBalancer service may be a better option. If you don’t want to expose your service to the world wide web for security reason, then use ClusterIP.