I use both Runbox and Fastmail. Of the two, I use Runbox more, because I use it to consolidate mail from different accounts, and I have been using it for over 10 years.

However, if I were to start over now, I would probably prefer Fastmail. The interface is more responsive, and they seem to be more actively developing the product.

Personally not sure about importing contacts, because I haven't tried it, but in terms of privacy, Runbox is hosted in Norway, and I believe Fastmail is based in Australia. Not sure what the exact implications are, but I think Norway may have stronger privacy protections.