Use Cases vs User Stories – Same Content, Different Outcome

In many discussions, I hear the statement:

“Use Cases and User Stories can contain the same information.”

At first glance, this sounds reasonable.
Both describe requirements. Both describe behavior. Both are used in modern software development.

But what happens if we take a real, non-trivial example and try to express it in both forms?

Let’s not argue in theory.
Let’s look at a concrete case.

A Real Use Case

The following is a real-world style Use Case for creating an order.
It is slightly anonymized, but structurally complete.

# UC-002: Create Order

**Primary Actor:** Back office agent  
**Secondary Actors:** Accounting, Quality Assurance  
**Goal:** Create a new order  
**Status:** Documented  

## Preconditions

- The user is logged in  
- The user has permission to create orders  
- The user has opened a customer detail view  

## Postconditions

### Success

- The order is successfully saved and assigned an order number  
- The created order is displayed  

### Failure

- An error message is shown explaining why the order could not be created  
- No order is created  

## Main Flow

1. The user clicks **Create Order**  
2. The system validates the customer (see GR-001)  
3. The system validates the location (see GR-002)  
4. The system validates the channel/capture type combination (see GR-003)  
5. The system creates the order with default values (see GR-004)  
6. The system validates the requested delivery date (see GR-005)  
7. The system sets delivery date and route based on the delivery calendar  
8. The system sets the delivery address (default customer delivery address)  
9. The system sets the status to **NEW**  
10. The system saves the order and locks it for the current user  
11. The system displays the created order  

## Alternative Flows

### 1a. Create order without preselected customer

1. The user clicks **Create Order**  
2. The system opens a new empty order  
3. The user selects a customer  
4. Continue with step 2 of the main flow  

### 2a. Customer validation fails

1. The system shows an error message (e.g., "Customer is inactive")  
2. The order is not created  

### 3a. Location validation fails

1. The system shows an error message (e.g., "Location is blocked")  
2. The order is not created  

### 6a. Delivery date validation fails (electronic capture)

1. The system still creates the order but marks it as **BLOCKED**  
2. The order must be manually released before further processing  

### 6b. Pickup order

1. The system skips delivery date validation  
2. The route is set to **PICKUP**  
3. Continue with step 8  

### 6c. Express / special order

1. The system only checks that the delivery date is not in the past  
2. The route is set to **EXPRESS**  
3. Continue with step 8  

### 6d. Location changed

1. The system checks if the customer has an active delivery schedule at the new location  
2. If yes: normal validation applies  
3. If no:
   - no validation is performed  
   - route is set to **EXPRESS**  

## Business Rules (Excerpt)

### GR-001: Customer Validation

- Customer must be active  
- No blocking flags on customer, organization, or group  

### GR-002: Location Validation

- Location must not be blocked  
- Delivery date must be after activation  

### GR-003: Channel / Capture Type Validation

- Some capture types require a channel  
- Some forbid a channel  
- Otherwise, the channel is optional  

### GR-004: Default Values

- Status = NEW  
- Order type = STANDARD  
- Capture type = phone  
- Channel = none  
- Delivery date = next possible  

### GR-005: Delivery Date Validation

- Standard: must exist in delivery calendar  
- Express: must not be in the past  
- Invalid electronic: order is blocked

Even in this slightly shortened form, you can already see:

a clear, end-to-end flow
explicit alternatives
centralized business rules
no ambiguity about system behavior

Everything is visible in one place.

Now let’s try the same with User Stories

We start with an Epic.

As a back office agent
I want to create orders
so that customer requests can be processed

Then we derive multiple User Stories.

As a back office agent
I want to create an order for a customer
so that I can capture a request

# Acceptance Criteria
- Customer must be active
- Location must be valid
- Channel and capture type must be consistent
- Order is created with default values
- Delivery date is validated
- Order is saved and displayed

As a back office agent
I want to see an error if the customer is invalid
so that I do not create incorrect orders

As a back office agent
I want orders with invalid delivery dates to be blocked
so that they are not processed incorrectly

As a back office agent
I want to create pickup orders
so that customers can collect goods

As a back office agent
I want the system to validate channel and capture type
so that order origin is consistent

To cover the full behavior, we would need:

many more User Stories
many more acceptance criteria
cross-references between them

What changed?

At a high level, both approaches describe the same domain.

But the structure is completely different.

With User Stories:

behavior is split across many items
flows are implicit
alternatives are scattered
rules are duplicated or hidden in criteria

To understand the system, you must mentally reconstruct the flow.

With the Use Case:

behavior is explicit
flow is visible end-to-end
alternatives are first-class citizens
rules are centralized and referenced

Can User Stories contain the same information?

Yes.
But only if you:

write many stories
add extensive acceptance criteria
maintain strong discipline
constantly align them

In practice, this leads to:

fragmentation
inconsistencies
loss of clarity

The information is still there.
But it is no longer visible as a whole.

Why this matters

For simple features, this difference is small.

But in real business systems:

rules interact
flows depend on each other
edge cases matter

In such environments:

missing connections cause bugs
hidden rules cause misunderstandings
implicit flows slow down development

This becomes even more critical when using AI.

AI works best with:

explicit structure
deterministic behavior
complete context

Use Cases provide exactly that.

Conclusion

User Stories and Use Cases can describe the same domain.
But they do not provide the same level of clarity.

User Stories describe intent.
Use Cases describe behavior.

When systems are simple, both work.

When systems become complex, the difference becomes obvious.

And when you try to express a full Use Case using User Stories,
you do not reduce complexity.

You just distribute it.