The difference is the sides
An omelette pan has low, gently rounded sides, de Buyer explains, so you can swirl and shake the eggs, roll the omelette and slide it straight onto a plate, the way a French omelette is made. A frying pan's sides flare more steeply; de Buyer shapes its own to keep the heat in the pan for searing, sautéing and pan-frying. Plenty of frying pans have sloped sides too, which is why the two names often get mixed up.
What each one cooks
An omelette pan is made for eggs, and de Buyer also suggests its own for frittatas, egg soufflés and crustless quiche, which can finish in the oven. A frying pan cooks eggs as well, along with meat, fish, vegetables and anything you sear or sauté, which is why it comes first in most kitchens.
Size and material
A small pan, around 8 inches, suits a two- or three-egg omelette and is light enough to shake: Made In's 8-inch stainless frying pan weighs 1.75 lb. Eggs release most easily from nonstick or ceramic, or from well-seasoned carbon steel, which is what de Buyer makes both its omelette and frying pans from. Stainless works too, once the pan and the butter are properly hot.
Which one to buy
Buy a frying pan first. If omelettes are a weekly habit, add a small omelette pan, or keep an 8-inch nonstick or carbon steel frying pan for eggs only, so its surface stays slick.
How these comparisons are made
Questions about this choice
Can I make an omelette in a frying pan?
Yes. A small frying pan with sloped sides makes a good omelette; an omelette pan's rounder edge just makes rolling it and sliding it out easier.
What size pan for an omelette?
Around 8 inches for two or three eggs. A bigger pan spreads the eggs too thin to roll; save a 10-inch pan for a frittata.