there are pros and cons for both breeds. Orpingtons are great, they're like fluffy chicken golden retrievers. They're docile and kind, and their roosters are generally not too aggressive. I myself have had seven orps and 1 rooster. The girls were wonderful eggers and did not go broody too often. The rooster was very aggressive unfortunately but he did a phenomenal job keeping the girls safe. They can be loud, I myself have not had any loud girls (although the rooster was very noisy).
Bantam eggs are actually considered a delicacy in some areas, as they are richer and much cuter than normal eggs *if eggs can be that cute*. Bantams are generally pretty sweet girls, and it doesn't matter as much if the rooster is aggressive XD because they are the size of your hand. Silkies especially are beautiful. In addition, bantams are extremely good if you have a small amount of space. I personally enjoy both breeds as they are both incredible for several reasons. Whichever breed suits your needs better is obviously the best choice. In addition, both breeds have a similar calm, sweet temperament.
If you want: Eggs, meat, more chicks
And if you have: Multiple nest boxes, larger coop area
then you should probably look for orps.
If you want: Adorable, Chick-sized all life, not aggressive/harmless, rich, small eggs
And if you have: Fewer nest boxes, limited space, neighbors who don't mind more crowing (because bantams often aren't sexed)
You should probably look for bantams.
2 edits:
1: Bantams do eat less/drink less. Def better for budget.
2: If you're just now starting with chickens, both breeds will work but orps will provide with a more well-rounded experience.
