I have toured on just about everything between 23 and 32 mm tires. I currently ride on 28 mm tires because the bike store was out of 32's when I last changed them.

I feel more stable on the wider tires. But the main reason I prefer them is that I get fewer flats. In seven years of riding 32 mm tires, I had exactly zero flats. In four or five seasons on 28 mm tires, one or two flats. During the many years I chose 23 and 25 mm tires, I usually had one flat per loaded tour.