I've been to both as well, as others mentioned, stanton is louder and orchard more quiet, orchard more refined food while stanton's is less complex, though both have interesting menus so I would say it depends on what you're looking for.
Going to both with a group of girls, I didn't notice much of a difference in price as far as the food was concerned. We were drinking wine by the bottle at orchard and cocktails at stanton which is why the stanton bill ended up slightly higher (compare ~$40 per bottle to ~$12 per cocktail).
at stanton I'd definitely request a table upstairs, much cosier than the downstairs
I agree with both responses that price is an issue at Stanton Social, however, if you are not taking this into consideration than I suggest going to Stanton Social. The dishes here are fun and small enough that you can try many of them. The menu is full of re-interpretations of classic comfort food served in small bite portions. Try the petite perogis with truffled creme, and the onion soup dumplings. The food is really fun here and I love going with friends who are also into food as we all get a kick out of the whimsy.
The only downfall with Stanton Social is that it gets really crowded. Try and get a seat upstairs and you will surely enjoy your meal!!
Mr. R. and I have not been to either. However, our daughter celebrated a birthday there with a large group of friends not long after they first opened. In fact, I'm often her restaurant selection guru, and it was I who suggested she go there. Her opinion was that the food was o.k., but nothing special. It's a small plates menu and she said the portions were so small that they had to order a boatload of dishes in order for her friends, especially the guys, to adequately fill up. That made for quite a steep bill. She and her friends have not been back since.
We have eaten at both in the last month. Very different experiences. Orchard is a higher quality meal, better service, more intimate atmosphere. SS is much louder and more energy. The dishes are hit or miss and the bill adds up quickly. A loud, rowdy meal with some good food and fun atmosphere is SS.
Orchard will serve you better if you are looking more for food and conversation vs people watching and booxing.