I have a mile gravel drive. I have used a box blade as a primary tool to keep it in a nice, smooth condition for 10 years, and it works fine. I have observed graders working and would certainly agree they can do a better job, for a lot more money. I have looked at land planes, and they too offer some real capabilities, for a lot more money. I picked up a regular rear blade a year ago for nothing, had it fixed and use it primarily for snow. I may use it once a year on the drive to bring some gravel back into the road bed, but that's all.
For a single tool for a gravel drive for someone trying to keep costs down, a box blade is the way to go. If you learn to rotate it a bit, you can do a lot with it. I rotate it forward and put the tines down fully to till my garden. Works.
I have added a Ratchet Rake for some brush control, but found it is also for minor grading jobs on the drive when I don't want to go hook up the heavy box blade.
For an old country boy like me, getting the job done as cheaply as possible is key. And for that I like my box blade.