My limited experience:
I have a box blade, for several years now. Only had a straight blade for ~1 year.
Both should be as heavy as they can be, as the 3 point has no down pressure to force the cutting action. Sometimes folks have had to buy different top links to get enough angle for the blade to work well (bite angle).
The two things I think my straight blade does better: it has a double jointed arm on it, so I can swing it out to a ditch, or near a fence, and keep my tractor out where I can maneuver it (or where is is safer). Also, it moves more material over (as opposed to filling in holes). This is really nice on long runs. My box blade is nicer for more specific movement of volume and filling in holes. The blade 'chatters' much easier than the box blade.
Scarifiers do a similar job as the various 'land plains' and 'conditioners' do: they bring the small aggregate back up, but probably don't do it as good as the conditioner equipment. You can overwork the soil and end up with only the larger gravel on top -- difficult at that point to get it butter smooth. That's the same affect as what happens after a road gets used and the aggregate 'settles in'.
At some point you may get the 'whoop-de whoops' in your drive. I am sure there is some method of measuring the distance of the blade to the rear wheels and dividing by the wheelbase and knowing the frequency (distance between) of them, but this is where the land plains and conditioners win out. I have been considering adding a gage wheel some distance behind my blade and seeing what affect it has. Maybe just adding some long chinks of angle iron along the sides would be good enough.
You do realize this will lead to further 'accessorizing' activity? Things like 'top and tilt'. I am not afraid to say -- their is no known cure for this. Resistance is futile, you will be implemented.
There are more specific tools that will do a better job at individual tasks, but the box blade is really difficult to beat as the first of these tools (or, if I can only own one tool). I would get one with a floating rear blade -- when the front is tilted way up, this makes a great smoothing (or final) pass.
Manual scarifiers work great (just tilt the box). Helps justify the top and tilt you wanted anyhow (and that can be used on all your implements as well as for hooking/unhooking implements).
