[Msquared]

Wider is always better on dry pavement, but you can probably get an even greater increase in grip from changing tires and compounds within the same than wider of the same kind of tire. Of course, if you get wider wheels and tires, you should get better tires too! Either way, in your climate I would recommend Michelin Pilot Sport 4S or Continental ExtremeContact Sport tires. They will be grippier in the dry and they are the two best rain tires you can buy, period.