Where our Santorini vs. Mykonos comparison looks at two similarly sized, similarly caldera-and-beach-focused islands, Crete is a genuinely different proposition — Greece's largest island by far, with its own cities, mountain ranges and a completely different pace.
Scale
Santorini can be reasonably covered, caldera villages included, inside a week. Crete is large enough to need its own dedicated week or more — it has multiple distinct regions (Chania, Heraklion, Rethymno, Lasithi), its own mountain ranges, and a road-trip-style way of travelling that has little in common with Santorini's compact, village-to-village pace.
What Crete offers that Santorini doesn't
Crete has Minoan-era palace sites at a much larger scale than Akrotiri (notably Knossos), genuine mountain scenery and gorges (including the well-known Samaria Gorge), a much longer and more varied coastline, and its own distinct culinary and wine traditions, generally more affordable than Santorini's.
What Santorini offers that Crete doesn't
The caldera itself, plainly — Crete has coastline and mountains, but nothing resembling Santorini's flooded volcanic crater and clifftop villages. If the specific caldera view is the point of your trip, Crete won't substitute for it.
Combining them
Both are reachable from Athens by air or ferry, and combining a few days on Santorini with a longer stretch on Crete is a common way to pair the iconic caldera view with a larger, more varied island experience — though note Crete generally needs considerably more time to do justice than Santorini does.
Spotted something out of date, or have a correction? Let us know — we'd rather fix it fast than leave it wrong.