Just started working in this area actually. I'm no expert, but I can give you what little information/impressions that I have.
Hannah's is mostly made up of small 2 person tables. Probably seats about 20 people. Some days it's very busy and other days there is lots of space.
Khyber Pass is a sitdown and has a lunch buffet for 10.95. Haven't tried this yet, but it does have some seating inside.
I haven't been to Sweetwater, but there should be lots of seating there as well.
Tokyo Lunch Box has no seating if I remember right.
Halsted Street Deli has some decent sandwiches. Probably seats about 20 and fills up fast if you don't beat the rush at lunch.
I Love Sushi- haven't tried it, but someone I know liked the Americhinese stuff they also serve. Looked like a gloopy Panda Express mess to me though. Some small amount of seating outside for maybe 10-15 people.
Sopraffina Marketcaffe- Another coworker also liked this one. A little more pricey than some of the other options down there, but I admit the food did look good. Inside they probably seat 15.