[excel] How can I concatenate strings in VBA?

This question comes from a comment under Range.Formula= in VBA throws a strange error.

I wrote that program by trial-and-error so I naturally tried + to concatenate strings.

But is & more correct than + for concatenating strings?

There is the concatenate function. For example

=CONCATENATE(E2,"-",F2)

But the & operator always concatenates strings. + often will work, but if there is a number in one of the cells, it won't work as expected.

The main (very interesting) difference for me is that:
"string" & Null -> "string"
while
"string" + Null -> Null

But that's probably more useful in database apps like Access.