I'm pretty sure that shooting buildings in attack mode counts FOR your hit%. For instance, my hit% in attack is double of that in fighter mode, despite me doing lot of ground strafing and spraying wildly after planes, mostly in my 110.
I also think, from a pure score (potato) point of view, that you will get better rank, if you got after the town instead of the hangars and field objects. Dropping bombs on a town, fully up, will give you a much higher hit%, for ordnance.
Lastly I think the points achieved for getting the actually destroying an object is neglible compared to the points given for causing the actual damage. This can't be told apart anymore with current score-pages, but if going back to tour 11 I can see that in bombers I recieved 99% of my bomber points for doing damage, but only 1% of the points were for actually destroying the object.
It could have changed since then, but I personally don't think so. Just look at the low amount of points a destruction of themap room gives (base capture). Something like 1010 points.