On this topic, see what I have said before
at:
http://thorncyclesforum.co.uk/index.php?topic=12883or at:
http://thorncyclesforum.co.uk/index.php?topic=13097A few more thoughts, as follows:
Years ago when someone asked me what they thought the better choice would be for touring in USA (where I live), it was easy to buy either 700c or 26 inch (559mm) tires. My response usually was that it was hard to find a good road touring tire that was wider than about 35 or 37 mm wide in 700c but it was hard to find a good road touring tire that was narrower than about 40mm in 26 inch. Thus, years ago I usually said if you want a wide tire, go with 26 or if you want a narrower tire go with 700c. That has since changed with the 29er bike craze, now you can find a good 700c tire of almost any width. But a narrower touring tire in 26 inch is still hard to find. Fortunately, for touring I am quite content with nothing narrower than 40mm in a 26 inch tire for touring.
I prefer 26 inch for touring for a different reason, all of my 700c bikes that have fenders have toe overlap, but none of my 26 inch bikes with fenders have toe overlap.
I have a 700c touring bike too (that has toe overlap) but I built that bike up for lighter touring, it has a Titanium frame. Thus, if I am going on a short trip and do not have a lot of weight, I would ride that bike instead.
If you have a coupled bike (S&S couplers or Ritchey Break Away) where you disassemble the bike to fit in a case small enough that airlines do not charge an oversize fee, 26 inch wheels fit in that size case easier than 700c. But that might not be as much of an issue in Europe. It is common in USA for airlines to charge an extra $150 USD for a one way flight if you have a case larger than 66 cm X 66 cm X 25 cm, but it is my understanding that airlines in Europe are much more bike friendly than airlines in USA and that it is easier to fly with a bike without that high of a fee fee for a bike.