I think it just depends on the recipe. I found that x-large eggs work best in my cornbread and waffle recipes. However, I think that they are interchangeable. You are right, that the media cooks stress using the best ingredients with no regard to cost.

Down here in FL, I can buy x-large eggs at the farmer's market for $3.50 a dozen and at the grocery store they cost about $2.00. Farmer market eggs are wonderfully fresh and that's why I sometime buy there.

If you are making something like biscotti that calls for 4 eggs and 2 yolks....extra large eggs would make a huge difference, but in a quick bread that calls for 2 eggs for 3 cups of flour or so...you won't know the difference. It's a matter of proportion.
Linda C

This is from the Baking Bites website:
A large egg, cracked, yields approximately 3 1/2 tablespoons of liquid. The yolk will be about 1 1/2 tbsp and the whites will be about 2 tbsp. An extra large egg will have about 4 tbsp of liquid inside, while a medium egg will have only 3 tbsp. These differences have no effect whatsoever on omelettes, hard boiled eggs or many other savory dishes, but they can actually have a big impact on baked goods.

With a recipe that calls for only one egg, the difference between sizes may not be noticeable. Substituting 4 extra large eggs in a recipe that only calls for 4 large eggs will add an extra half-an-egg in volume to your recipe. This changes the ratios given in the recipe and can mean that youÂll end up with a drier or eggier finished product, one not quite as good as would have been achieved with the right sized eggs. Extra large eggs can be a good deal when it comes to eggs for breakfast, but if you know youÂre going to be dealing with a lot of eggs for baking (especially in egg-heavy recipes), it is often best just to buy the size of egg dictated in the recipe itself (large, if not directly specified).

The link below is an interesting discussion about this topic and the lady asking the question even brings up The Barefoot Contessa.

Hope this helps! Judi

Here is a link that might be useful: Large VS Extra Large Eggs

Cooks states that all eggs used in their recipes are large.

If I'm only using one egg i don't worry about extra volume, but if there are 3 or 4 I would measure. I've started keeping a box of large eggs on hand for cooking/baking, but use XL for breakfast.

Thanks for your input. So it's about what I figured: Know your recipe and measure the volume of the eggs. Since I live alone, don't eat that many eggs, and don't get the opportunity to feed others that much I don't want to consider having to buy and keep two sizes of eggs, so I'll just fiddle around with the large ones.

Judi: thanks for the information and also the link you provided. I'm surprised I never knew that forum existed even though I receive several emails daily from King Arthur/Cook Illustrated, etc., etc. (The count today was 6!) You all have spoiled me so much with all the great things I've learned from CF that I think I'd hesitate to have to pay for another one!

Nancy