Neither is reliably cheaper. Comparison sites charge a booking fee and negotiate lower rates; operators avoid the fee and often start from a higher published price. The only way to know is to price both.
That sounds like a non-answer, and it is the honest one. What is useful is knowing what each adds, so you can tell which is likely to win for your particular trip.
What does a comparison site add?
Rates negotiated on volume, and a single place to see the options. They bring operators a steady stream of bookings, and that buying power usually earns a lower rate than an individual customer gets.
They also solve the discovery problem. Finding every operator serving your airport, pricing each one and comparing them manually takes considerably longer than the fee is worth to most people.
The cost is that fee, typically a flat amount at checkout. Flat fees hurt short bookings disproportionately — a few pounds on a weekend matters, the same few pounds on a fortnight does not.
What does booking direct add?
No comparison fee, and a direct relationship if something goes wrong.
That second point is underrated. When a flight is delayed or a registration needs changing, dealing with the operator directly removes a step. With a comparison booking you may need to establish who holds the money before anyone can act.
Direct booking is also where repeat-customer rates live. Operators reward returning customers because acquiring you cost them money and keeping you does not.
The first booking is usually cheaper through a comparison site. The third one with the same operator is frequently cheaper direct.
How do I compare them properly?
Open both checkouts and compare the final totals. Listing prices tell you nothing useful.
Price the comparison site total, fees included
Price the same operator direct, fees included
Check whether either rate is flexible or fixed, since that changes what you are buying
Check whether cancellation cover has been pre-ticked on either
Two minutes, and it settles the question for that trip. Do not assume the answer carries over — it varies by operator and by date.
When is direct more likely to win?
You have used that operator before and have a returning-customer rate
Short trips, where a flat comparison fee is a large share of a small total
You are on their mailing list, which is where genuine codes arrive
Business travel, where a direct account simplifies VAT receipts
When is a comparison site more likely to win?
A first booking at an airport you do not know
Longer trips, where the negotiated daily rate outweighs a flat fee
Peak dates, where seeing all availability at once matters more than the fee
When you genuinely do not know which operators serve the airport
Does it matter for amendments?
Slightly, and it is worth knowing before you need it. Changing a registration or a date is usually handled by whoever took the booking.
With a direct booking that is one phone call. With a comparison booking it may be two, or a form, depending on how the site handles it. Neither is difficult, but the direct route is shorter when you are standing at a barrier.
What about refunds?
Refunds come from whoever took the money. If you booked through a comparison site, they hold it and they issue it.
That is worth checking on your bank statement if a problem arises and you cannot remember which route you used. The name on the transaction tells you where to start.
Does cashback change the calculation?
It can tip a close comparison, and it works with both routes. Cashback sits outside the booking itself, so it generally stacks where a second discount code would not.
The rates differ between the two routes though, and not predictably. A comparison site may pay well one month and nothing the next, while an operator pays steadily or not at all.
Check before clicking through rather than afterwards. Going direct to a site first and then trying to apply cashback does not track, and that is the commonest reason people do not receive it.
A practical approach
Use a comparison site to find out who serves your airport and roughly what things cost. Then, if you are likely to use that operator again, check their direct price before booking.
After a trip, keep the confirmation and the receipt. The rebooking offer that follows is often the best rate that operator gives anyone, and it only reaches people who booked directly or joined the mailing list.
Compare both routes for your dates at Manchester, Birmingham or Luton rather than assuming either wins.
