I often describe 26 inch wheeled touring bikes as an Expedition bikes and in many ways bike running 26 inch wheels can be more versatile than a 700c equipped bike if you find you want to run wider tyres (my Cascade will run a knobby 2.0). 26 inch wheels are just a little tougher than similarly built 700c wheels, and for some riders the slightly smaller wheels makes the frame geometry work out.

As far as speed goes... if you are loaded down and riding a 26 inch wheeled bike on 1.5's there is not going to be much difference in roll out to a touring bike with 700-32 tyres and the higher volume tyres may offer a little more ride comfort due to them being able to be run at a wider pressure range.

There is also a small gearing advantage with 26 inch wheels if you are looking for the lowest gearings possible unless of course you also happen to use a 20 inch wheeled tourer and then finding adequate top gearing is more work.