IOW, Belgians are nicer people (in general), the Swiss live in a nicer country
Being a Dutchspeaking native you might have trouble in Frenchspeaking parts of Belgium, there is still a lot of animosity between Flanders and Walony.
When we visited Brussels some years ago in some places people wouldn't even look at us until the discovered we were not from Flanders but Dutch (I guess the reverse would go for Frenchmen in Flanders). In Switzerland that's not a problem.
Belgium is of course closer to the Netherlands, which makes it easier and cheaper to go home quickly if needed.