IMHO (at least), Andy's is a much better store than Bobak's, by a lot.
I've been meaning to say something lately about how Polish markets are the great unsung heros of Chicago eating. To me, they are like good and gooder (and I've never discovered a Polish market that's been less than good). I mean take Bobak's, on the scale of things, it's not bad, but on the Polish market scale, there's just so many great ones, it's hard to compare. All of these stores feature outstanding dairy and eggs, assorted high quality fresh cheeses and kefirs (a real treat when you can find it, are places that make the Highlander fresh sheep's milk*); of course there are the sausages and deli stuff, depending on the place it will be big or bigger selection; likewise the meat counter will be good, most of the places have Amish chickens and the like; pickles, pickles in the barrel are as god as anywhere in Chicago; usually excellent prepared foods, and breads, some bake their own, others get from assorted local bakeries. The quality is just so beyond about any other market in Chicago. If you enjoy eating, you should shop regularly at Polish markets.
Like I say, Andy's is one of the better markets, great deli, great bakery. Avenues on Belmont at Oak Park Ave is another good one on the North side. I shop a lot at Kolatch (2445 N. Harlem). The deli is relatively small, but this is a place for prepared foods and breads especially. (Kinda the opposite of Avenues, which has a huge deli but sucky prepared foods).
*Alas, I have only found fresh made sheep's milk cheese at Southside Polish markets.
Think Yiddish, Dress British - Advice of Evil Ronnie to me.