Airside and landside are different bookings
Incheon Airport lists transit hotels inside the duty-free area and capsule-hotel facilities at the terminal transport centres. A traveller who has passed immigration cannot treat an airside transit hotel as an ordinary arrival hotel. Confirm terminal, immigration status and access instructions before booking.
Late check-in and shuttle details decide the nearby option
A hotel described as airport-area accommodation can still require a scheduled shuttle or taxi. Check the final shuttle, pickup point, reception hours and terminal served. For a very late arrival, a slightly higher room price can be the lower-risk option when it removes an uncertain transfer.
Do not sacrifice the whole Seoul stay
An airport-area room is usually an arrival-night or departure-night solution, not a base for repeated Seoul sightseeing. If transport still runs and the city hotel accepts the arrival time, continuing once may avoid changing accommodation the next morning. Use the airport finder with the post-immigration time.