The Méribel Valley pass gives you access to around 150km of pistes between Les Allues, Méribel, Méribel Village and Méribel-Mottaret. For many people, that's plenty for a week's skiing, particularly if you're a beginner or intermediate skier and don't feel the need to cover huge distances every day.
The 3 Vallées pass opens up around 600km of interconnected pistes across Méribel, Courchevel, La Tania, Les Menuires, Saint-Martin-de-Belleville, Val Thorens, Orelle and Brides-les-Bains. Méribel sits right in the middle of the area, so it's a particularly good base if you want to ski in different valleys during your holiday.
The price difference is worth thinking about, and for a strong skier who enjoys exploring, that extra flexibility can be good value. For a family with young children who will spend most of the week around Méribel, it may not be necessary.
There are also cheaper options for beginners, four-hour passes for shorter days, Family Flex discounts and a 20% Saturday discount on the 3 Vallées day pass.
The most expensive pass isn't automatically the best one. Think about how you actually want to ski before buying.