IMHO "slick" is more important than "thin" if you're primarily on pavement. 2" slicks at fairly high pressure will roll well and will give you a higher error margin with cracks and potholes and so on. The other factor is your ride distance; unless you're doing over 10mi or so, it really won't matter at much. Remember, "any bike is better than no bike", so you're already on second-order optimization here.