Two Questions re: wheels and brakes

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Is there much difference between a bike with 26x1.5" tires and one with 700x32c tires with regards to commuting? I have always ridden hybrids wtih 26" tires for commuting.

Are disc brakes dramatically safer in wet or emergency conditions or are a good set of cantilevers and pads sufficient on the road?

My commute is 9 miles one way direct, or 5 miles after a 4 mile light rail trip.