I find a Longtail the most versatile, partly because it rides a lot like a "normal" bike.
A Bakfiets is heavy, but has many advantages, like the fact that a 30+ kilo bike makes a good bike rack for all the others, and in a non-cycling city, pretty much un-nickable so the inbuilt lock suffices which is very convenient.
I find either preferable to trailers because they take up remarkably little storage space and I don't have to worry about hitching them; just get on and go. By the same token if I'm out on the Longtail spontaneous errands are simple because extra capacity is already there.