Slot filling is the process where the Dialogflow agent continues collecting information from the end-user until the end-user has provided data for each of the required parameters. On Dialogflow ES, there is no way to limit the maximum number of retries. This slot filling issue is now resolved in the Dialogflow CX.
Console UX
Dialogflow ES is mostly a text-based. Since Dialogflow physician data CX has a visual editor, visual graphs showing conversation paths and text forms for configurations improve user experience.
Prebuilt Agents
Prebuilt agents are a collection of agents provided by Dialogflow for everyday use cases. These agents can establish a base for building conversations for ticket booking, hotel booking, car rental, etc. Both the Dialogflow CX and ES have this feature for better usage. Prebuilt agents include intents and entities for their use cases.
Agent/Project
Dialogflow ES supports only one agent per project, while the Dialogflow CX supports 100 agents/project.
CX is an advanced agent type suitable for large or very complex agents with flows, pages, and state handlers to control the conversation paths. Simultaneously, ES is a standard agent type ideal for small to medium and straightforward to moderately complex agents where the intents and contexts are used to control conversation paths.