I haven't seen this question asked before. Would you rather have a Canon 17-55mm or an ef-s 60mm macro, Sigma 30mm 1.4, 18-55mm IS and a 50mm 1.8? (For a crop camera, of course) Together, these four lenses cost about the same as the 17-55mm.
One lens-no switching for this range
4 lens set pros:
Lower light ability (for moving subjects)
Possibly better IQ with 60mm and 30mm
4 Different lens characteristics
Lighter setup when choosing just one or probably even two lenses
I have found the 18-55mm IS a great little lens when paired with a 580exii. I am loving my new 60mm macro. I'm planning to get a Sigma 30mm soon or sell everything for the 17-55mm. Right now I'm mostly taking pictures of our 8 month old daughter, but I'm also doing some landscapes/cityscapes and party pictures. But I was wondering which choice you would make based on the type of shots you take.