Outward opening external door
First off, I found a great discussion thread on the topic here. The best comment was clearly "Creates a clear threshold that magical creatures cannot cross without being invited".
The other one was how it was easier for emergency services to break down the door (and for police, HMRC, etc, too) if it is inward opening.
It seems to be the case that in the UK, and apparently the US, external doors normally open inwards. Some other countries (Sweden was mentioned) do not follow this rule.
I used to have a house that opened right on to the street, and for that an outward opening door (especially with no window) would have been, err, fun. But here I am opening on to our drive.
My reasoning is simple, and applies to both internal and external doors - I want to maximise the space I have been graciously given by my wife for my "man cave", and outward opening doors help with that. The internal door uses the same space as a cupboard in the utility room, so a no brainer - not taking away any extra space doing that. The external door is more interesting.
I can see two obvious downsides to this, and ways to address them:-
One is quite important - the hinges are exposed and someone could break them, cut them off, pop the pins out, or some such. Obviously this would trip the alarm, but a smash and grab could get stuff. The answer is, however, very simple - hinge bolts. They stop the hinge side being forced like that. Only issue is why they are labelled "Window Hinge Bolts"???
The only other real concern (and magical creatures are not an issue, AFAIK), is catching in the wind. I am not sure I need to worry - it will simply be a matter of being careful, but I plan to try installing a concealed door closer in the top of the door limiting it to 110° and closing the door nicely. I may try this on internal door first to see how well it works.
Sandra has a concern if she was to park too close on the drive, but to be honest, I do not see the size of a door being an issue, even if a 3ft wide one.