I will be doing a fully-loaded tour of the Oregon coast next month; my current tire choices are either my commuter set (Panaracer TServ PT 700x32c front/Specialized Infinity 700x35c rear) or my road set (Scwalbe Durano 700x25c front and rear). I will be riding on pavement 98% of the time, so dirt/gravel is not really a concern. The Scwalbes give me a lot less rolling resistance but I'm not sure how they will hold up to full loads over time.
BTW, I weigh about 205 lbs, will be on a Surly Cross Check with an estimated 40lbs. divided between front and rear panniers.