Tires definitely can affect speed. Lighter tires are faster. Tires with less rolling resistance are faster. And wider tires may be faster, as long as they don't increase weight a lot. Do you know what the weight difference is between your Bontrager and Gatorskins? If the Gators are wire bead, they might be heavier. Personally if I had to choose between two tires that weighed about the same but were different widths, I would take the wider tire. However, some tires are just slow because of high rolling resistance due to the rubber compounds they use and tread. I tried some Panaracer Pasela TGs for a while and had to get rid of them because they felt so slow. They were not that much heavier than the tires they replaced, but rolled so slow that they felt like they had glue on the treads.