Is a central US 3PL better than a coastal one for shipping speed and cost?

Often, if your customers are spread across the country. Simpl Fulfillment ships every order from one warehouse in Austin, Texas, so Austin is the example here. Take one ZIP code in each of the 20 largest US metro areas: from Austin none is in USPS zone 8, the farthest and most expensive band any of them reaches; from Los Angeles nine are, and from Newark, New Jersey, six. Zones follow distance and set ground postage, so central narrows the spread of what you pay to those cities; transit time tends to follow distance too, though a zone chart doesn't measure delivery days. Central is still not automatically cheaper or faster than a coastal warehouse near most of your customers.

What the USPS zone chart shows

Ground postage rises by zone, and zones rise with distance from the warehouse. From Austin, the farthest of those 20 sample ZIPs (in New York, Boston, Philadelphia, San Francisco and Seattle) are zone 7. Newark's six zone-8 ZIPs are all on the West Coast and in the Southwest, yet its average zone across the twenty is slightly lower than Austin's because so many large metros sit close to it. Among those sample ZIPs, central lowers your worst case and evens the spread; it doesn't always lower your average. Other ZIPs in the same metro can land a zone higher or lower.

When central wins, and when coastal does

• Your customers are spread across the country. From Austin, Simpl's estimated ground delivery runs from 1–2 business days to Dallas–Fort Worth and Houston to 3–5 to Los Angeles, Miami, New York and Seattle (estimates; actual times vary by carrier, service and ZIP).
• Most of your orders go to one coast. A warehouse on that coast sits closer to those customers, so it can beat central on speed and postage to them; the real test is each 3PL's quotes and service estimates for the same shipments. How much a central warehouse gives up depends on where the rest of your orders go.
• You need fast delivery everywhere and ship real volume. A second warehouse starts to make sense, at the price of splitting inventory and inbound shipments.

The practical check: pull a few months of ship-to ZIP codes and look them up on a zone chart from each warehouse you're considering. See how USPS shipping zones work, and the full estimate table from Austin on our Texas 3PL page.