How does sulfasalazine measure up to other 5-asa drugs such as asacol (mesalamine) and colazal for ulcerative colitis?

Similar for UC. These are all fairly effective for mild ulcerative colitis. None of them have long-term benefit for crohn's disease (aka regional enteritis).
SFZ vs Asacol (mesalamine) Sfz is the best drug for intestinal disease, certainly "1" for regional enteritis and crohn's in the si. However, colonic bacteria breaks down sfz, and Asacol (mesalamine) is not. So for large bowel disease Asacol (mesalamine) is preferred for reasons of efficacy.