If you want large eggs from the getgo, ISA Browns are the breed of choice, IMO. They large consistently large to extra large eggs from about the week after they come into lay. The largest egg I have weighed from one of them was 112 grams! They do wear out faster, as they seem to lay basically every day unless they are molting, but if it is good size eggs you are after, you can't go wrong with them. Make sure you feed them well. Vitamin supplements in the water (Rooster Booster I highly recommend. Fixed a lameness problem I had with a Barred Rock hen), good, higher protein feed (I feed mine Purina flock raiser), some forage and mealworms, oyster shell.
Generally my consistently smallest eggs came from boutique breeds like Jungle Fowl and Crested Cream Legbar. They are fun, but in the end, I am in this for eggs and meat, not to feed cute looking freeloaders. Neither breed has been good for either, IME. Plus they are way more human aggressive/distant or at least less respect than the ISA Browns and Bielefelders I have had. Same with Barred Rocks. I hated my Barred Rocks. I didn't eat them but I did manage to rehome them. Never having them again. Eggs medium, temperament bad, health problems more than my other breeds.
TL;DR - Get ISA Browns for good sized eggs and human friendly and curious chickens. I am having my first go with Bielefelders and they are so sweet and non-aggressive (including the cockrel), I think in the future I will only have them in their own pens away from other breeds, but they do get huge, FAST.