Really depends on what you like to cook. Ina Garten focuses on American and European recipes for the most part.
Ottolenghi became famous with middle-eastern / levantine recipes, and expanded to include broadly asian flavors and techniques without making “asian dishes” (and most recently Mexican because someone on his team has mexican heritage).
So it boils down to what kind of food you cook, or want to cook / eat.
(People get flustered by his ingredient lists, but if you cook any kind of asian or middle eastern food already, you probably have 75% of the ingredients, and are not thrown by a list of spices. Simple was his attempt to have no more than 10 ingredients in a recipe, but Jerusalem and both the Plenty books have better recipes.)
There are a few Ottolenghi threads you can browse, the Guardian has a pile of his book recipes, as does his website and if you google any recipe name (check EYB or the Amazon previews).
