A single lane out of South China may carry a dozen advertised services in any given week, and a booking goes to exactly one of them. Rate is part of that decision and rarely the deciding part, because the cheapest service on a lane is frequently the one with the longest rotation, the tightest cut-off or the least chance of a container being released on the day you need it. The criteria below are applied in this order.
The first pass is a filter rather than a comparison: which carriers can physically take this cargo from this port. Special equipment is the usual constraint, since flat racks, open tops and high cubes are not evenly distributed and a carrier with no suitable boxes at that origin depot cannot serve you whatever the rate says. Dangerous goods narrow the field further, because acceptance differs by class, by UN number and by port pair, and some combinations are refused outright.
Next comes schedule fit, which is not the same as the shortest advertised transit. What matters is whether the cut-off is achievable given when the factory will genuinely finish and when documents can realistically be complete, and whether arrival lands inside the window the consignee can receive. A service sailing two days later, direct, with a comfortable documentation cut-off, regularly beats a nominally faster string that demands paperwork nobody at either end can produce in time.
Then reliability, assessed at the level of the individual service rather than the carrier as a whole. The same operator can run a dependable direct string and a transhipment service that misconnects routinely, and the published transit time distinguishes neither. What matters is how that specific string has performed recently, how the carrier behaves when it is overbooked, and whether it blanks sailings at short notice or announces them far enough ahead for cargo to be replanned.
Equipment and space position at origin weigh as heavily as price. A carrier running a container deficit at a port releases boxes slowly and prioritises its own contract accounts, so a competitive spot rate there can mean a booking that never confirms. A carrier repositioning empties out of the same port wants the cargo and will hold space. We also check the condition of what the depot is releasing, because a leaking or previously contaminated box creates a claim, not a saving.
Destination terms are a carrier decision rather than simply a rate line. Free time at destination, detention rates once it expires, how quickly the line issues and releases documents, whether telex release works reliably on that trade, and whether the electronic bill your bank or consignee will accept is supported. At a congested discharge port, the difference between seven and fourteen free days can outweigh every rate difference on the table by a wide margin.
How a carrier behaves when something goes wrong is a criterion in its own right. Whether its destination office answers enquiries directly or routes everything back through origin. How it handles a booking amendment or a change of discharge port, and whether it re-rates the entire shipment to do so. How it treats a damage claim and what evidence it demands. None of this appears on a rate sheet; it is learned by moving cargo and keeping notes.
Cost then enters as a total rather than a headline. A contract rate with allocation is often worth paying for over a lower spot rate with no space priority, particularly ahead of a peak or a long factory closure, because a rate without space is an expensive delay. Against that, a long commitment on a falling market carries its own cost. For most shippers the sensible position is base allocation with carriers that perform, and flexibility on the balance.
Finally, the decision is recorded — which carrier, which service, and why — so it can be compared against what actually happened. Transit performance, equipment availability, document turnaround and exception handling all shift, sometimes within a single quarter, and the right carrier mix on a lane in spring is not automatically the right one in autumn. Reviewing that record is what stops a booking habit from outliving the reason it was formed.
