A fair question. For the shake of the discussion we will have to divide this up into discussing France and SPG (Spain-Portugal-Greece).

I would consider my point IV (collapsing banks in a country which threatens to leave), the most important point which distinguish these two options.

France:
As Cyrille has pointed out, it is not quite clear how to leave the Euro with out discussing it first and for France the Banks did not collapse when Sarkozy hinted that France could leave the Euro. But that is France, and I guess that many people simply agree with my point III (The French fundamental are sound).

SPG:
Maybe you know better, but I feel that here my point IV is fully applicable. this obviously leaves the problem of how to organize a withdrawal form the Euro.

That is why I also added the 'other options part'. Issuing an additional currency could be the best option for SPG.