Oh, man. Every year there's someone claiming that bigger fatter tires are actually faster somehow, and every year there's someone who actually tries it and finds the obvious - that a 2.0" tire is definitely slower than a much thinner 25c tires in the same size and of the same quality.

Can't say what I would choose if I had carpal tunnel, my bike was already 35 pounds, etc. Jeff Poulin's first response post, in my opinion, was really the most accurate -

2.0 will have better ride quality.
1.6 will be faster.