I'm kinda like you, in that it took me a long time to look at air-seeders. Here's what I've found for differences between the two:

• Much more trash clearance when seeding into stubble. For a hoe type opener, they'll clear as much and maybe more than my Haybuster 8000s did, but pull way easier and are much faster. In the box drill with hoe openers, the CIH 7200 was probably about the best you could do and there is night and day difference between what the Concord will clear and what the hoe drills did.
• Much more consistent seeding depth because the seeding tool always weighs the same. When the box drill was full, the packers sunk more and pushed the seed deeper. As the drill emptied out, the seed would end up shallower.
• Much more precise distribution of seed across the width of the tool. PAMI did some studies on this, I believe and they concluded that an air-seeder is within 2% -- much better than you will find with a box drill.
• Much easier to calibrate the rate with a central metering system than it ever was with the fluted feed drills. Also easier to change the rate and remain confident that the extra gets spread evenly across the entire width.
• Cleanout between varieties or at the end of season is a snap with an air cart. Not so with the box drills.
• When using box drills and integral transports, you need to be mindful of having the drills less than half full if a move is involved. Not as big a concern with an air cart if you watch your speed when transporting.
• With my CIH drills, I had to unhook, hook and then unhook, hook every time I moved. It involved locking the cylinders up and coupling and uncoupling hydraulics a couple times for every move. I really don't even need to leave the tractor to fold, move, and unfold.
• Filling the cart can be done with one set of the product truck and is mostly unattended. Much nicer than multiple sets with the tender and always having to mind the product spout.
• It is possible to treat the seed as you fill the cart and eliminate contaminating all the tender equipment. Very tough to do that with box drills.
• Extremely easy to check for blocked runs every time you fill or any other time you happen to stop. Not so with the box drills