I only have a few days on each, but IMO:

1) A push. The boom isn't much of an issue IMO, but it is one less thing to worry about. On the other hand, the boom does allow for better sail trim.
2) The 5.0 is less likely to pitchpole
3) Another push, they are about even.
4) The H16 is probably a little better in this regard. Parts are very easy to find and are dirt cheap since so many H16's have been produced. For this same reason the initial purchase price of a used H16 with likely be cheaper as well.
5) Another push.