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Cash wins on price for most Southwest flights because buying points costs about what they are worth, or more. Points win on flexibility, and they win outright when you only need a small top-up to finish a booking. Which matters more depends on the trip.

Here is the comparison, category by category.

Round 1: Price

Southwest sells Rapid Rewards points for 3 cents each at the standard price. During sales, One Mile at a Time has reported discounts of 35%, 45%, or 50% depending on the member, which works out to 1.95, 1.65, or 1.5 cents per point. The sale discount applies to purchases of at least 3,000 points.

What is a point worth when you spend it? Southwest prices awards in line with cash fares, so the value stays in a tight range. Frequent Miler uses 1.3 cents per point. One Mile at a Time estimates 1.1 to 1.5 cents.

So you would pay 1.5 cents or more for something that returns about 1.3 cents. On a full ticket, cash is cheaper.

Winner: cash.

Round 2: Flexibility

Southwest doesn't charge change fees on either ticket type. The difference is what you get back when you cancel:

• Points booking: Frequent Miler notes you can cancel with no fee up to 10 minutes before departure, and the points return to your account immediately. One Mile at a Time adds that anyone can use the redeposited points at any future time.
• Cash booking: canceling issues a travel credit that must be used for a future flight.

If your schedule is solid, this does not matter. If you are booking around a tour that could reroute, a client meeting that might move, or a family situation, it matters a lot.

Winner: points.

Round 3: What you earn

A cash ticket earns Rapid Rewards points, and those base points count toward the Companion Pass. Frequent Miler sets that requirement at 135,000 qualifying points per calendar year.

Purchased points do not count toward the Companion Pass. And because Points.com processes the sale, your credit card will not treat the purchase as airfare.

Winner: cash.

Round 4: Speed and simplicity

Paying cash is one step. Buying points is two steps: purchase, then book once they arrive. If the fare or points price moves in between, you may need more points than you bought.

Winner: cash.

See your Rapid Rewards discount and compare.

Three sample trips

These are illustrative numbers to show the method. Use your own fare and points price.

Trip 1: A routine round trip

Fare: $236. Points price: 18,000. You have no points.

• Value per point: $236 divided by 18,000 is 1.31 cents.
• Cost to buy 18,000 points at 50% off: $270.

Cash wins by $34, and you earn points on the fare.

Trip 2: You are nearly there

Fare: $236. Points price: 18,000. You have 15,500 points.

• Buy 3,000 points at 50% off: about $45.
• Pay cash: $236, and your 15,500 points sit unused.

Points win by about $191. A top-up changes the comparison because most of the ticket is paid with points you already own.

Trip 3: An uncertain date

Fare: $310. Points price: 23,500. You have 8,000 points. The trip may be postponed.

• Buy 15,500 points at 50% off: about $233.
• Pay cash: $310.

Check the points price for your flight.

Points come out about $77 cheaper here, and if the trip is called off, you can put the points back into your account for any future flight, for anyone you choose to book. With a cash ticket, you would hold a travel credit. If your discount is only 35%, the same points cost about $302, and the price advantage is gone, though the flexibility remains.

The scorecard

• Lowest price on a full ticket: cash, in most cases.
• Small gap to close: points.
• Plans that might change: points.
• Working toward Companion Pass: cash.
• Booking for other people from one balance: points.

How to decide in one minute

• Divide the cash fare by the points price.
• Check your cost per point at the discount your account shows.
• If your cost is lower than the value, points win on price.
• If it is higher, ask whether the flexibility is worth the difference to you.

Good to know either way

• You can buy up to 60,000 points a day, with no annual limit, according to One Mile at a Time.
• Rapid Rewards points do not expire.
• Southwest's Cash + Points option exists, but Frequent Miler says it yields poor value per point.
• Free checked bags now depend on your fare type, elite status, or a Southwest credit card. Add bag costs to both sides of the comparison.