Check if service exists in bash (CentOS and Ubuntu)

What is the best way in bash to check if a service is installed? It should work across both Red Hat (CentOS) and Ubuntu?

Thinking:

service="mysqld"if [ -f "/etc/init.d/$service" ]; then    # mysqld service existsfi

Could also use the service command and check the return code.

service mysqld statusif [ $? = 0 ]; then    # mysqld service existsfi

What is the best solution?