Originally Posted by
johnread
Going with a wider tire and running lower pressures will make your bike handle slower and less efficiently, so going that way won't help you get up the hills faster or with less effort.
Going 25, or even 28 mm will not make handling any worse, nor make any noticeable difference going up a hill. We're talking commuting here. Not racing.
Getting drop bars and using different groups of muscles could make a greater impact.