We have a few vito's and the VW equivalent at work.
Hate to say it but the Merc's are crap.  The van's get a real flogging and the Vito's are rattly, noisy and always breaking.  Mechanically there ok but it's things like sliding doors not opening, then when I do give them the appropriate encouragement they won't shut.  Door's not locking etc.
I can't speak on the quality of the car's I'd love to own one!  I also can't really speak on the quality of the cheaper vans.  But I was very disappointed with the vitto.
See Will-i-am ,  Vito's aren't that good!