Euro
I see your point, but the "probability" is that some unfortunate soul will be stopped by the French Police for being over 3.5T (actual or permissable!), breaking the speed limit without stickers. They might be lucky and just get a verbal from an officer who doesn't see it as an issue or they might get a fine. As we all know claiming ignorance of the law (and it's interpretation) and trying to tell an officer it's not an issue wouldn,t help!
As always it's personal preference.....just like speeding is in the UK. Myself, I've got my stickers and will try to stick to the limit!