I grew up in Milwaukee I have had both Solly's and Kopps burgers, and by far would recommend anyone visiting Milwaukee to try a burger from Kopps over Solly's. You will not leave hungry! I also highly recommend the fries, they have great flavor. The only con is that there is no table seating...about 5 standing tables to eat at at the Layton location. You can eat inside the Kopps in Brookfield, but they only have benches to sit on. Everyone I bring from out of town has enjoyed their Kopps burger. Another surprise is their buffalo chicken sandwich. It comes with a surpisingly spicy buffalo sauce, chopped celery, and bleu cheese all with a nice piece of grilled chicken breast. My wife loves it. Custard is great, highly recommend the tiramisu and grasshopper! Make sure you grab a lot of napkins!!
Pros: huge, tasty burgers, fries, and buffalo chicken sandwich, multiple locations, good/quick service
Cons: No in restaurant seating; eat in car or take home