SA probably has the best customer service of all the 1911 entry level makers now. Colt's is also pretty good.
SA pros: lifetime warranty with paid shipping, wide variety of models.
Colt pros: Decent warranty with paid shipping, less variety, cachet of the Colt name.
Sig pros: Good variety, well finished.
Kimber pros: Seem well finished, dehorned very well. Lots of variety.
SA cons: The fit and finish of the SA guns I've seen lately is not as great.
Colt cons: Colts have very sharp edges, especially on the dust cover and front of the slide.
Sig cons: Unique slide profile means regular 1911 holsters often don't fit.
Kimber cons: Supposed to have bad customer service.